diff --git a/src/class32/Code01_IndexTree.java b/src/class32/Code01_IndexTree.java
index f7d5eca..4c4bdab 100644
--- a/src/class32/Code01_IndexTree.java
+++ b/src/class32/Code01_IndexTree.java
@@ -2,16 +2,19 @@ package class32;
 
 public class Code01_IndexTree {
 
+	// 下标从1开始！
 	public static class IndexTree {
 
 		private int[] tree;
 		private int N;
 
+		// 0位置弃而不用！
 		public IndexTree(int size) {
 			N = size;
 			tree = new int[N + 1];
 		}
 
+		// 1~index 累加和是多少？
 		public int sum(int index) {
 			int ret = 0;
 			while (index > 0) {
@@ -21,6 +24,9 @@ public class Code01_IndexTree {
 			return ret;
 		}
 
+		// index & -index : 提取出index最右侧的1出来
+		// index :           0011001000
+		// index & -index :  0000001000
 		public void add(int index, int d) {
 			while (index <= N) {
 				tree[index] += d;
diff --git a/src/class32/Code04_AC2.java b/src/class32/Code04_AC2.java
index fc915bc..e684de3 100644
--- a/src/class32/Code04_AC2.java
+++ b/src/class32/Code04_AC2.java
@@ -17,6 +17,7 @@ public class Code04_AC2 {
 		public boolean endUse;
 		public Node fail;
 		public Node[] nexts;
+
 		public Node() {
 			endUse = false;
 			end = null;
@@ -39,8 +40,7 @@ public class Code04_AC2 {
 			for (int i = 0; i < str.length; i++) {
 				index = str[i] - 'a';
 				if (cur.nexts[index] == null) {
-					Node next = new Node();
-					cur.nexts[index] = next;
+					cur.nexts[index] = new Node();
 				}
 				cur = cur.nexts[index];
 			}
@@ -53,14 +53,12 @@ public class Code04_AC2 {
 			Node cur = null;
 			Node cfail = null;
 			while (!queue.isEmpty()) {
-				// 当前节点弹出，
-				// 当前节点的所有后代加入到队列里去，
-				// 当前节点给它的子去设置fail指针
-				// cur -> 父亲
+				// 某个父亲，cur
 				cur = queue.poll();
 				for (int i = 0; i < 26; i++) { // 所有的路
-					if (cur.nexts[i] != null) { // 找到所有有效的路
-						cur.nexts[i].fail = root; //
+					// cur -> 父亲  i号儿子，必须把i号儿子的fail指针设置好！
+					if (cur.nexts[i] != null) { // 如果真的有i号儿子
+						cur.nexts[i].fail = root;
 						cfail = cur.fail;
 						while (cfail != null) {
 							if (cfail.nexts[i] != null) {
@@ -75,6 +73,7 @@ public class Code04_AC2 {
 			}
 		}
 
+		// 大文章：content
 		public List<String> containWords(String content) {
 			char[] str = content.toCharArray();
 			Node cur = root;
@@ -92,7 +91,7 @@ public class Code04_AC2 {
 				cur = cur.nexts[index] != null ? cur.nexts[index] : root;
 				follow = cur;
 				while (follow != root) {
-					if(follow.endUse) {
+					if (follow.endUse) {
 						break;
 					}
 					// 不同的需求，在这一段之间修改
@@ -115,8 +114,8 @@ public class Code04_AC2 {
 		ac.insert("he");
 		ac.insert("abcdheks");
 		// 设置fail指针
-		ac.build();	
-		
+		ac.build();
+
 		List<String> contains = ac.containWords("abcdhekskdjfafhasldkflskdjhwqaeruv");
 		for (String word : contains) {
 			System.out.println(word);
diff --git a/src/class33/Hash.java b/src/class33/Hash.java
index 552191b..2c54b7d 100644
--- a/src/class33/Hash.java
+++ b/src/class33/Hash.java
@@ -29,7 +29,7 @@ public class Hash {
 		}
 		System.out.println("=======");
 
-		String algorithm = "SHA";
+		String algorithm = "MD5";
 		Hash hash = new Hash(algorithm);
 
 		String input1 = "zuochengyunzuochengyun1";
diff --git a/src/class37/Code01_CountofRangeSum.java b/src/class37/Code01_CountofRangeSum.java
index e8f1292..d79fa02 100644
--- a/src/class37/Code01_CountofRangeSum.java
+++ b/src/class37/Code01_CountofRangeSum.java
@@ -164,18 +164,17 @@ public class Code01_CountofRangeSum {
 	}
 
 	public static int countRangeSum2(int[] nums, int lower, int upper) {
+		// 黑盒，加入数字（前缀和），不去重，可以接受重复数字
+		// < num , 有几个数？
 		SizeBalancedTreeSet treeSet = new SizeBalancedTreeSet();
 		long sum = 0;
 		int ans = 0;
 		treeSet.add(0);// 一个数都没有的时候，就已经有一个前缀和累加和为0，
 		for (int i = 0; i < nums.length; i++) {
 			sum += nums[i];
-			// sum    i结尾的时候[lower, upper]
-			// 之前所有前缀累加和中，有多少累加和落在[sum - upper, sum - lower]
-			// 查 ？ < sum - lower + 1   a
-			// 查 ?  < sum - upper    b
-			// a - b
-			
+			// [sum - upper, sum - lower]
+			// [10, 20] ?
+			// < 10 ?  < 21 ?   
 			long a = treeSet.lessKeySize(sum - lower + 1);
 			long b = treeSet.lessKeySize(sum - upper);
 			ans += a - b;
diff --git a/src/class37/Code04_QueueReconstructionByHeight.java b/src/class37/Code04_QueueReconstructionByHeight.java
new file mode 100644
index 0000000..2513402
--- /dev/null
+++ b/src/class37/Code04_QueueReconstructionByHeight.java
@@ -0,0 +1,265 @@
+package class37;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.LinkedList;
+
+// 本题测试链接：https://leetcode.com/problems/queue-reconstruction-by-height/
+public class Code04_QueueReconstructionByHeight {
+
+	public static int[][] reconstructQueue1(int[][] people) {
+		int N = people.length;
+		Unit[] units = new Unit[N];
+		for (int i = 0; i < N; i++) {
+			units[i] = new Unit(people[i][0], people[i][1]);
+		}
+		Arrays.sort(units, new UnitComparator());
+		ArrayList<Unit> arrList = new ArrayList<>();
+		for (Unit unit : units) {
+			arrList.add(unit.k, unit);
+		}
+		int[][] ans = new int[N][2];
+		int index = 0;
+		for (Unit unit : arrList) {
+			ans[index][0] = unit.h;
+			ans[index++][1] = unit.k;
+		}
+		return ans;
+	}
+
+	public static int[][] reconstructQueue2(int[][] people) {
+		int N = people.length;
+		Unit[] units = new Unit[N];
+		for (int i = 0; i < N; i++) {
+			units[i] = new Unit(people[i][0], people[i][1]);
+		}
+		Arrays.sort(units, new UnitComparator());
+		SBTree tree = new SBTree();
+		for (int i = 0; i < N; i++) {
+			tree.insert(units[i].k, i);
+		}
+		LinkedList<Integer> allIndexes = tree.allIndexes();
+		int[][] ans = new int[N][2];
+		int index = 0;
+		for (Integer arri : allIndexes) {
+			ans[index][0] = units[arri].h;
+			ans[index++][1] = units[arri].k;
+		}
+		return ans;
+	}
+
+	public static class Unit {
+		public int h;
+		public int k;
+
+		public Unit(int height, int greater) {
+			h = height;
+			k = greater;
+		}
+	}
+
+	public static class UnitComparator implements Comparator<Unit> {
+
+		@Override
+		public int compare(Unit o1, Unit o2) {
+			return o1.h != o2.h ? (o2.h - o1.h) : (o1.k - o2.k);
+		}
+
+	}
+
+	public static class SBTNode {
+		public int value;
+		public SBTNode l;
+		public SBTNode r;
+		public int size;
+
+		public SBTNode(int arrIndex) {
+			value = arrIndex;
+			size = 1;
+		}
+	}
+
+	public static class SBTree {
+		private SBTNode root;
+
+		private SBTNode rightRotate(SBTNode cur) {
+			SBTNode leftNode = cur.l;
+			cur.l = leftNode.r;
+			leftNode.r = cur;
+			leftNode.size = cur.size;
+			cur.size = (cur.l != null ? cur.l.size : 0) + (cur.r != null ? cur.r.size : 0) + 1;
+			return leftNode;
+		}
+
+		private SBTNode leftRotate(SBTNode cur) {
+			SBTNode rightNode = cur.r;
+			cur.r = rightNode.l;
+			rightNode.l = cur;
+			rightNode.size = cur.size;
+			cur.size = (cur.l != null ? cur.l.size : 0) + (cur.r != null ? cur.r.size : 0) + 1;
+			return rightNode;
+		}
+
+		private SBTNode maintain(SBTNode cur) {
+			if (cur == null) {
+				return null;
+			}
+			int leftSize = cur.l != null ? cur.l.size : 0;
+			int leftLeftSize = cur.l != null && cur.l.l != null ? cur.l.l.size : 0;
+			int leftRightSize = cur.l != null && cur.l.r != null ? cur.l.r.size : 0;
+			int rightSize = cur.r != null ? cur.r.size : 0;
+			int rightLeftSize = cur.r != null && cur.r.l != null ? cur.r.l.size : 0;
+			int rightRightSize = cur.r != null && cur.r.r != null ? cur.r.r.size : 0;
+			if (leftLeftSize > rightSize) {
+				cur = rightRotate(cur);
+				cur.r = maintain(cur.r);
+				cur = maintain(cur);
+			} else if (leftRightSize > rightSize) {
+				cur.l = leftRotate(cur.l);
+				cur = rightRotate(cur);
+				cur.l = maintain(cur.l);
+				cur.r = maintain(cur.r);
+				cur = maintain(cur);
+			} else if (rightRightSize > leftSize) {
+				cur = leftRotate(cur);
+				cur.l = maintain(cur.l);
+				cur = maintain(cur);
+			} else if (rightLeftSize > leftSize) {
+				cur.r = rightRotate(cur.r);
+				cur = leftRotate(cur);
+				cur.l = maintain(cur.l);
+				cur.r = maintain(cur.r);
+				cur = maintain(cur);
+			}
+			return cur;
+		}
+
+		private SBTNode insert(SBTNode root, int index, SBTNode cur) {
+			if (root == null) {
+				return cur;
+			}
+			root.size++;
+			int leftAndHeadSize = (root.l != null ? root.l.size : 0) + 1;
+			if (index < leftAndHeadSize) {
+				root.l = insert(root.l, index, cur);
+			} else {
+				root.r = insert(root.r, index - leftAndHeadSize, cur);
+			}
+			root = maintain(root);
+			return root;
+		}
+
+		private SBTNode get(SBTNode root, int index) {
+			int leftSize = root.l != null ? root.l.size : 0;
+			if (index < leftSize) {
+				return get(root.l, index);
+			} else if (index == leftSize) {
+				return root;
+			} else {
+				return get(root.r, index - leftSize - 1);
+			}
+		}
+
+		private void process(SBTNode head, LinkedList<Integer> indexes) {
+			if (head == null) {
+				return;
+			}
+			process(head.l, indexes);
+			indexes.addLast(head.value);
+			process(head.r, indexes);
+		}
+
+		public void insert(int index, int value) {
+			SBTNode cur = new SBTNode(value);
+			if (root == null) {
+				root = cur;
+			} else {
+				if (index <= root.size) {
+					root = insert(root, index, cur);
+				}
+			}
+		}
+
+		public int get(int index) {
+			SBTNode ans = get(root, index);
+			return ans.value;
+		}
+
+		public LinkedList<Integer> allIndexes() {
+			LinkedList<Integer> indexes = new LinkedList<>();
+			process(root, indexes);
+			return indexes;
+		}
+
+	}
+
+	// 通过以下这个测试，
+	// 可以很明显的看到LinkedList的插入和get效率不如SBTree
+	// LinkedList需要找到index所在的位置之后才能插入或者读取，时间复杂度O(N)
+	// SBTree是平衡搜索二叉树，所以插入或者读取时间复杂度都是O(logN)
+	public static void main(String[] args) {
+		// 功能测试
+		int test = 10000;
+		int max = 1000000;
+		boolean pass = true;
+		LinkedList<Integer> list = new LinkedList<>();
+		SBTree sbtree = new SBTree();
+		for (int i = 0; i < test; i++) {
+			int randomIndex = (int) (Math.random() * (i + 1));
+			int randomValue = (int) (Math.random() * (max + 1));
+			list.add(randomIndex, randomValue);
+			sbtree.insert(randomIndex, randomValue);
+		}
+		for (int i = 0; i < test; i++) {
+			if (list.get(i) != sbtree.get(i)) {
+				pass = false;
+				break;
+			}
+		}
+		System.out.println("功能测试是否通过 : " + pass);
+
+		// 性能测试
+		test = 50000;
+		list = new LinkedList<>();
+		sbtree = new SBTree();
+		long start = 0;
+		long end = 0;
+
+		start = System.currentTimeMillis();
+		for (int i = 0; i < test; i++) {
+			int randomIndex = (int) (Math.random() * (i + 1));
+			int randomValue = (int) (Math.random() * (max + 1));
+			list.add(randomIndex, randomValue);
+		}
+		end = System.currentTimeMillis();
+		System.out.println("LinkedList插入总时长(毫秒) ： " + (end - start));
+
+		start = System.currentTimeMillis();
+		for (int i = 0; i < test; i++) {
+			int randomIndex = (int) (Math.random() * (i + 1));
+			list.get(randomIndex);
+		}
+		end = System.currentTimeMillis();
+		System.out.println("LinkedList读取总时长(毫秒) : " + (end - start));
+
+		start = System.currentTimeMillis();
+		for (int i = 0; i < test; i++) {
+			int randomIndex = (int) (Math.random() * (i + 1));
+			int randomValue = (int) (Math.random() * (max + 1));
+			sbtree.insert(randomIndex, randomValue);
+		}
+		end = System.currentTimeMillis();
+		System.out.println("SBTree插入总时长(毫秒) : " + (end - start));
+
+		start = System.currentTimeMillis();
+		for (int i = 0; i < test; i++) {
+			int randomIndex = (int) (Math.random() * (i + 1));
+			sbtree.get(randomIndex);
+		}
+		end = System.currentTimeMillis();
+		System.out.println("SBTree读取总时长(毫秒) :  " + (end - start));
+
+	}
+
+}
diff --git a/src/class38/Code01_AppleMinBags.java b/src/class38/Code01_AppleMinBags.java
new file mode 100644
index 0000000..54d4182
--- /dev/null
+++ b/src/class38/Code01_AppleMinBags.java
@@ -0,0 +1,47 @@
+package class38;
+
+public class Code01_AppleMinBags {
+
+	public static int minBags(int apple) {
+		if (apple < 0) {
+			return -1;
+		}
+		int bag6 = -1;
+		int bag8 = apple / 8;
+		int rest = apple - 8 * bag8;
+		while (bag8 >= 0 && rest < 24) {
+			int restUse6 = minBagBase6(rest);
+			if (restUse6 != -1) {
+				bag6 = restUse6;
+				break;
+			}
+			rest = apple - 8 * (--bag8);
+		}
+		return bag6 == -1 ? -1 : bag6 + bag8;
+	}
+
+	// 如果剩余苹果rest可以被装6个苹果的袋子搞定，返回袋子数量
+	// 不能搞定返回-1
+	public static int minBagBase6(int rest) {
+		return rest % 6 == 0 ? (rest / 6) : -1;
+	}
+
+	public static int minBagAwesome(int apple) {
+		if ((apple & 1) != 0) { // 如果是奇数，返回-1
+			return -1;
+		}
+		if (apple < 18) {
+			return apple == 0 ? 0 : (apple == 6 || apple == 8) ? 1
+					: (apple == 12 || apple == 14 || apple == 16) ? 2 : -1;
+		}
+		return (apple - 18) / 8 + 3;
+	}
+
+	public static void main(String[] args) {
+		for(int apple = 1; apple < 100;apple++) {
+			System.out.println(apple + " : "+ minBags(apple));
+		}
+
+	}
+
+}
diff --git a/src/class38/Code02_EatGrass.java b/src/class38/Code02_EatGrass.java
new file mode 100644
index 0000000..200abcd
--- /dev/null
+++ b/src/class38/Code02_EatGrass.java
@@ -0,0 +1,45 @@
+package class38;
+
+public class Code02_EatGrass {
+
+	// n份青草放在一堆
+	// 先手后手都绝顶聪明
+	// string "先手" "后手"
+	public static String winner1(int n) {
+		// 0  1  2  3 4
+		// 后 先 后 先 先
+		if (n < 5) { // base case
+			return (n == 0 || n == 2) ? "后手" : "先手";
+		}
+		// n >= 5 时
+		int base = 1; // 当前先手决定吃的草数
+		// 当前是先手在选
+		while (base <= n) {
+			// 当前一共n份草，先手吃掉的是base份，n - base 是留给后手的草
+			// 母过程 先手 在子过程里是 后手
+			if (winner1(n - base).equals("后手")) {
+				return "先手";
+			}
+			if (base > n / 4) { // 防止base*4之后溢出
+				break;
+			}
+			base *= 4;
+		}
+		return "后手";
+	}
+
+	public static String winner2(int n) {
+		if (n % 5 == 0 || n % 5 == 2) {
+			return "后手";
+		} else {
+			return "先手";
+		}
+	}
+
+	public static void main(String[] args) {
+		for (int i = 0; i <= 50; i++) {
+			System.out.println(i + " : " + winner1(i));
+		}
+	}
+
+}
diff --git a/src/class38/Code03_MSumToN.java b/src/class38/Code03_MSumToN.java
new file mode 100644
index 0000000..81e6bad
--- /dev/null
+++ b/src/class38/Code03_MSumToN.java
@@ -0,0 +1,41 @@
+package class38;
+
+public class Code03_MSumToN {
+
+	public static boolean isMSum1(int num) {
+		for (int i = 1; i <= num; i++) {
+			int sum = i;
+			for (int j = i + 1; j <= num; j++) {
+				if (sum + j > num) {
+					break;
+				}
+				if (sum + j == num) {
+					return true;
+				}
+				sum += j;
+			}
+		}
+		return false;
+	}
+
+	public static boolean isMSum2(int num) {
+		if (num < 3) {
+			return false;
+		}
+		return (num & (num - 1)) != 0;
+	}
+
+	public static void main(String[] args) {
+		for (int num = 1; num < 200; num++) {
+			System.out.println(num + " : " + isMSum1(num));
+		}
+		System.out.println("test begin");
+		for (int num = 1; num < 5000; num++) {
+			if (isMSum1(num) != isMSum2(num)) {
+				System.out.println("Oops!");
+			}
+		}
+		System.out.println("test end");
+
+	}
+}
diff --git a/src/class38/Code04_MoneyProblem.java b/src/class38/Code04_MoneyProblem.java
new file mode 100644
index 0000000..0ea4e4a
--- /dev/null
+++ b/src/class38/Code04_MoneyProblem.java
@@ -0,0 +1,131 @@
+package class38;
+
+public class Code04_MoneyProblem {
+
+	// int[] d d[i]：i号怪兽的武力
+	// int[] p p[i]：i号怪兽要求的钱
+	// ability 当前你所具有的能力
+	// index 来到了第index个怪兽的面前
+
+	// 目前，你的能力是ability，你来到了index号怪兽的面前，如果要通过后续所有的怪兽，
+	// 请返回需要花的最少钱数
+	public static long process(int[] d, int[] p, int ability, int index) {
+		if (index == d.length) {
+			return 0;
+		}
+		if (ability < d[index]) {
+			return p[index] + process(d, p, ability + d[index], index + 1);
+		} else { // 可以贿赂，也可以不贿赂
+			return 
+					Math.min(
+							p[index] + process(d, p, ability + d[index], index + 1),
+						    process(d, p, ability, index + 1)
+							);
+		}
+	}
+
+	public static long func1(int[] d, int[] p) {
+		return process(d, p, 0, 0);
+	}
+
+	public static long func2(int[] d, int[] p) {
+		int sum = 0;
+		for (int num : d) {
+			sum += num;
+		}
+		long[][] dp = new long[d.length + 1][sum + 1];
+		for (int i = 0; i <= sum; i++) {
+			dp[0][i] = 0;
+		}
+		for (int cur = d.length - 1; cur >= 0; cur--) {
+			for (int hp = 0; hp <= sum; hp++) {
+				// 如果这种情况发生，那么这个hp必然是递归过程中不会出现的状态
+				// 既然动态规划是尝试过程的优化，尝试过程碰不到的状态，不必计算
+				if (hp + d[cur] > sum) {
+					continue;
+				}
+				if (hp < d[cur]) {
+					dp[cur][hp] = p[cur] + dp[cur + 1][hp + d[cur]];
+				} else {
+					dp[cur][hp] = Math.min(p[cur] + dp[cur + 1][hp + d[cur]], dp[cur + 1][hp]);
+				}
+			}
+		}
+		return dp[0][0];
+	}
+
+	public static long func3(int[] d, int[] p) {
+		int sum = 0;
+		for (int num : p) {
+			sum += num;
+		}
+		// dp[i][j]含义：
+		// 能经过0～i的怪兽，且花钱为j（花钱的严格等于j）时的武力值最大是多少？
+		// 如果dp[i][j]==-1，表示经过0～i的怪兽，花钱为j是无法通过的，或者之前的钱怎么组合也得不到正好为j的钱数
+		int[][] dp = new int[d.length][sum + 1];
+		for (int i = 0; i < dp.length; i++) {
+			for (int j = 0; j <= sum; j++) {
+				dp[i][j] = -1;
+			}
+		}
+		// 经过0～i的怪兽，花钱数一定为p[0]，达到武力值d[0]的地步。其他第0行的状态一律是无效的
+		dp[0][p[0]] = d[0];
+		for (int i = 1; i < d.length; i++) {
+			for (int j = 0; j <= sum; j++) {
+				// 可能性一，为当前怪兽花钱
+				// 存在条件：
+				// j - p[i]要不越界，并且在钱数为j - p[i]时，要能通过0～i-1的怪兽，并且钱数组合是有效的。
+				if (j >= p[i] && dp[i - 1][j - p[i]] != -1) {
+					dp[i][j] = dp[i - 1][j - p[i]] + d[i];
+				}
+				// 可能性二，不为当前怪兽花钱
+				// 存在条件：
+				// 0~i-1怪兽在花钱为j的情况下，能保证通过当前i位置的怪兽
+				if (dp[i - 1][j] >= d[i]) {
+					// 两种可能性中，选武力值最大的
+					dp[i][j] = Math.max(dp[i][j], dp[i - 1][j]);
+				}
+			}
+		}
+		int ans = 0;
+		// dp表最后一行上，dp[N-1][j]代表：
+		// 能经过0～N-1的怪兽，且花钱为j（花钱的严格等于j）时的武力值最大是多少？
+		// 那么最后一行上，最左侧的不为-1的列数(j)，就是答案
+		for (int j = 0; j <= sum; j++) {
+			if (dp[d.length - 1][j] != -1) {
+				ans = j;
+				break;
+			}
+		}
+		return ans;
+	}
+
+	public static int[][] generateTwoRandomArray(int len, int value) {
+		int size = (int) (Math.random() * len) + 1;
+		int[][] arrs = new int[2][size];
+		for (int i = 0; i < size; i++) {
+			arrs[0][i] = (int) (Math.random() * value) + 1;
+			arrs[1][i] = (int) (Math.random() * value) + 1;
+		}
+		return arrs;
+	}
+
+	public static void main(String[] args) {
+		int len = 10;
+		int value = 20;
+		int testTimes = 1000000;
+		for (int i = 0; i < testTimes; i++) {
+			int[][] arrs = generateTwoRandomArray(len, value);
+			int[] d = arrs[0];
+			int[] p = arrs[1];
+			long ans1 = func1(d, p);
+			long ans2 = func2(d, p);
+			long ans3 = func3(d, p);
+			if (ans1 != ans2 || ans2 != ans3) {
+				System.out.println("oops!");
+			}
+		}
+
+	}
+
+}
diff --git a/src/class39/Code01_DifferentBTNum.java b/src/class39/Code01_DifferentBTNum.java
new file mode 100644
index 0000000..4655e3c
--- /dev/null
+++ b/src/class39/Code01_DifferentBTNum.java
@@ -0,0 +1,66 @@
+package class39;
+
+public class Code01_DifferentBTNum {
+
+//	k(0) = 1, k(1) = 1
+//
+//	k(n) = k(0) * k(n - 1) + k(1) * k(n - 2) + ... + k(n - 2) * k(1) + k(n - 1) * k(0)
+//	或者
+//	k(n) = c(2n, n) / (n + 1)
+//	或者
+//	k(n) = c(2n, n) - c(2n, n-1)
+
+	public static long num1(int N) {
+		if (N < 0) {
+			return 0;
+		}
+		if (N < 2) {
+			return 1;
+		}
+		long[] dp = new long[N + 1];
+		dp[0] = 1;
+		dp[1] = 1;
+		for (int i = 2; i <= N; i++) {
+			for (int leftSize = 0; leftSize < i; leftSize++) {
+				dp[i] += dp[leftSize] * dp[i - 1 - leftSize];
+			}
+		}
+		return dp[N];
+	}
+
+	public static long num2(int N) {
+		if (N < 0) {
+			return 0;
+		}
+		if (N < 2) {
+			return 1;
+		}
+		long a = 1;
+		long b = 1;
+		for (int i = 1, j = N + 1; i <= N; i++, j++) {
+			a *= i;
+			b *= j;
+			long gcd = gcd(a, b);
+			a /= gcd;
+			b /= gcd;
+		}
+		return (b / a) / (N + 1);
+	}
+
+	public static long gcd(long m, long n) {
+		return n == 0 ? m : gcd(n, m % n);
+	}
+
+	public static void main(String[] args) {
+		System.out.println("test begin");
+		for (int i = 0; i < 15; i++) {
+			long ans1 = num1(i);
+			long ans2 = num2(i);
+			if (ans1 != ans2) {
+				System.out.println("Oops!");
+			}
+		}
+		System.out.println("test finish");
+	}
+
+}
diff --git a/src/class39/Code02_10Ways.java b/src/class39/Code02_10Ways.java
new file mode 100644
index 0000000..1068ce2
--- /dev/null
+++ b/src/class39/Code02_10Ways.java
@@ -0,0 +1,92 @@
+package class39;
+
+import java.util.LinkedList;
+
+public class Code02_10Ways {
+
+	public static long ways1(int N) {
+		int zero = N;
+		int one = N;
+		LinkedList<Integer> path = new LinkedList<>();
+		LinkedList<LinkedList<Integer>> ans = new LinkedList<>();
+		process(zero, one, path, ans);
+		long count = 0;
+		for (LinkedList<Integer> cur : ans) {
+			int status = 0;
+			for (Integer num : cur) {
+				if (num == 0) {
+					status++;
+				} else {
+					status--;
+				}
+				if (status < 0) {
+					break;
+				}
+			}
+			if (status == 0) {
+				count++;
+			}
+		}
+		return count;
+	}
+
+	public static void process(int zero, int one, LinkedList<Integer> path, LinkedList<LinkedList<Integer>> ans) {
+		if (zero == 0 && one == 0) {
+			LinkedList<Integer> cur = new LinkedList<>();
+			for (Integer num : path) {
+				cur.add(num);
+			}
+			ans.add(cur);
+		} else {
+			if (zero == 0) {
+				path.addLast(1);
+				process(zero, one - 1, path, ans);
+				path.removeLast();
+			} else if (one == 0) {
+				path.addLast(0);
+				process(zero - 1, one, path, ans);
+				path.removeLast();
+			} else {
+				path.addLast(1);
+				process(zero, one - 1, path, ans);
+				path.removeLast();
+				path.addLast(0);
+				process(zero - 1, one, path, ans);
+				path.removeLast();
+			}
+		}
+	}
+
+	public static long ways2(int N) {
+		if (N < 0) {
+			return 0;
+		}
+		if (N < 2) {
+			return 1;
+		}
+		long a = 1;
+		long b = 1;
+		long limit = N << 1;
+		for (long i = 1; i <= limit; i++) {
+			if (i <= N) {
+				a *= i;
+			} else {
+				b *= i;
+			}
+		}
+		return (b / a) / (N + 1);
+	}
+
+	public static void main(String[] args) {
+		System.out.println("test begin");
+		for (int i = 0; i < 10; i++) {
+			long ans1 = ways1(i);
+			long ans2 = ways2(i);
+			if (ans1 != ans2) {
+				System.out.println("Oops!");
+			}
+		}
+		System.out.println("test finish");
+	}
+
+}
diff --git a/src/class39/Code03_RotateMatrix.java b/src/class39/Code03_RotateMatrix.java
new file mode 100644
index 0000000..ee3f956
--- /dev/null
+++ b/src/class39/Code03_RotateMatrix.java
@@ -0,0 +1,44 @@
+package class39;
+
+public class Code03_RotateMatrix {
+
+	public static void rotate(int[][] matrix) {
+		int a = 0;
+		int b = 0;
+		int c = matrix.length - 1;
+		int d = matrix[0].length - 1;
+		while (a < c) {
+			rotateEdge(matrix, a++, b++, c--, d--);
+		}
+	}
+
+	public static void rotateEdge(int[][] m, int a, int b, int c, int d) {
+		int tmp = 0;
+		for (int i = 0; i < d - b; i++) {
+			tmp = m[a][b + i];
+			m[a][b + i] = m[c - i][b];
+			m[c - i][b] = m[c][d - i];
+			m[c][d - i] = m[a + i][d];
+			m[a + i][d] = tmp;
+		}
+	}
+
+	public static void printMatrix(int[][] matrix) {
+		for (int i = 0; i != matrix.length; i++) {
+			for (int j = 0; j != matrix[0].length; j++) {
+				System.out.print(matrix[i][j] + " ");
+			}
+			System.out.println();
+		}
+	}
+
+	public static void main(String[] args) {
+		int[][] matrix = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 }, { 13, 14, 15, 16 } };
+		printMatrix(matrix);
+		rotate(matrix);
+		System.out.println("=========");
+		printMatrix(matrix);
+
+	}
+
+}
diff --git a/src/class39/Code04_PrintMatrixSpiralOrder.java b/src/class39/Code04_PrintMatrixSpiralOrder.java
new file mode 100644
index 0000000..27b8f30
--- /dev/null
+++ b/src/class39/Code04_PrintMatrixSpiralOrder.java
@@ -0,0 +1,53 @@
+package class39;
+
+public class Code04_PrintMatrixSpiralOrder {
+
+	public static void spiralOrderPrint(int[][] matrix) {
+		int tR = 0;
+		int tC = 0;
+		int dR = matrix.length - 1;
+		int dC = matrix[0].length - 1;
+		while (tR <= dR && tC <= dC) {
+			printEdge(matrix, tR++, tC++, dR--, dC--);
+		}
+	}
+
+	public static void printEdge(int[][] m, int tR, int tC, int dR, int dC) {
+		if (tR == dR) {
+			for (int i = tC; i <= dC; i++) {
+				System.out.print(m[tR][i] + " ");
+			}
+		} else if (tC == dC) {
+			for (int i = tR; i <= dR; i++) {
+				System.out.print(m[i][tC] + " ");
+			}
+		} else {
+			int curC = tC;
+			int curR = tR;
+			while (curC != dC) {
+				System.out.print(m[tR][curC] + " ");
+				curC++;
+			}
+			while (curR != dR) {
+				System.out.print(m[curR][dC] + " ");
+				curR++;
+			}
+			while (curC != tC) {
+				System.out.print(m[dR][curC] + " ");
+				curC--;
+			}
+			while (curR != tR) {
+				System.out.print(m[curR][tC] + " ");
+				curR--;
+			}
+		}
+	}
+
+	public static void main(String[] args) {
+		int[][] matrix = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 },
+				{ 13, 14, 15, 16 } };
+		spiralOrderPrint(matrix);
+
+	}
+
+}
diff --git a/src/class39/Code05_ZigZagPrintMatrix.java b/src/class39/Code05_ZigZagPrintMatrix.java
new file mode 100644
index 0000000..09089cb
--- /dev/null
+++ b/src/class39/Code05_ZigZagPrintMatrix.java
@@ -0,0 +1,43 @@
+package class39;
+
+public class Code05_ZigZagPrintMatrix {
+
+	public static void printMatrixZigZag(int[][] matrix) {
+		int tR = 0;
+		int tC = 0;
+		int dR = 0;
+		int dC = 0;
+		int endR = matrix.length - 1;
+		int endC = matrix[0].length - 1;
+		boolean fromUp = false;
+		while (tR != endR + 1) {
+			printLevel(matrix, tR, tC, dR, dC, fromUp);
+			tR = tC == endC ? tR + 1 : tR;
+			tC = tC == endC ? tC : tC + 1;
+			dC = dR == endR ? dC + 1 : dC;
+			dR = dR == endR ? dR : dR + 1;
+			fromUp = !fromUp;
+		}
+		System.out.println();
+	}
+
+	public static void printLevel(int[][] m, int tR, int tC, int dR, int dC,
+			boolean f) {
+		if (f) {
+			while (tR != dR + 1) {
+				System.out.print(m[tR++][tC--] + " ");
+			}
+		} else {
+			while (dR != tR - 1) {
+				System.out.print(m[dR--][dC++] + " ");
+			}
+		}
+	}
+
+	public static void main(String[] args) {
+		int[][] matrix = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 } };
+		printMatrixZigZag(matrix);
+
+	}
+
+}
diff --git a/src/class39/Code06_PrintStar.java b/src/class39/Code06_PrintStar.java
new file mode 100644
index 0000000..02f2b5d
--- /dev/null
+++ b/src/class39/Code06_PrintStar.java
@@ -0,0 +1,46 @@
+package class39;
+
+public class Code06_PrintStar {
+
+	public static void printStar(int N) {
+		int leftUp = 0;
+		int rightDown = N - 1;
+		char[][] m = new char[N][N];
+		for (int i = 0; i < N; i++) {
+			for (int j = 0; j < N; j++) {
+				m[i][j] = ' ';
+			}
+		}
+		while (leftUp <= rightDown) {
+			set(m, leftUp, rightDown);
+			leftUp += 2;
+			rightDown -= 2;
+		}
+		for (int i = 0; i < N; i++) {
+			for (int j = 0; j < N; j++) {
+				System.out.print(m[i][j] + " ");
+			}
+			System.out.println();
+		}
+	}
+
+	public static void set(char[][] m, int leftUp, int rightDown) {
+		for (int col = leftUp; col <= rightDown; col++) {
+			m[leftUp][col] = '*';
+		}
+		for (int row = leftUp + 1; row <= rightDown; row++) {
+			m[row][rightDown] = '*';
+		}
+		for (int col = rightDown - 1; col > leftUp; col--) {
+			m[rightDown][col] = '*';
+		}
+		for (int row = rightDown - 1; row > leftUp + 1; row--) {
+			m[row][leftUp + 1] = '*';
+		}
+	}
+
+	public static void main(String[] args) {
+		printStar(8);
+	}
+
+}
diff --git a/src/class40/Code01_LongestSumSubArrayLengthInPositiveArray.java b/src/class40/Code01_LongestSumSubArrayLengthInPositiveArray.java
new file mode 100644
index 0000000..a2389fa
--- /dev/null
+++ b/src/class40/Code01_LongestSumSubArrayLengthInPositiveArray.java
@@ -0,0 +1,91 @@
+package class40;
+
+public class Code01_LongestSumSubArrayLengthInPositiveArray {
+
+	public static int getMaxLength(int[] arr, int K) {
+		if (arr == null || arr.length == 0 || K <= 0) {
+			return 0;
+		}
+		int left = 0;
+		int right = 0;
+		int sum = arr[0];
+		int len = 0;
+		while (right < arr.length) {
+			if (sum == K) {
+				len = Math.max(len, right - left + 1);
+				sum -= arr[left++];
+			} else if (sum < K) {
+				right++;
+				if (right == arr.length) {
+					break;
+				}
+				sum += arr[right];
+			} else {
+				sum -= arr[left++];
+			}
+		}
+		return len;
+	}
+
+	// for test
+	public static int right(int[] arr, int K) {
+		int max = 0;
+		for (int i = 0; i < arr.length; i++) {
+			for (int j = i; j < arr.length; j++) {
+				if (valid(arr, i, j, K)) {
+					max = Math.max(max, j - i + 1);
+				}
+			}
+		}
+		return max;
+	}
+
+	// for test
+	public static boolean valid(int[] arr, int L, int R, int K) {
+		int sum = 0;
+		for (int i = L; i <= R; i++) {
+			sum += arr[i];
+		}
+		return sum == K;
+	}
+
+	// for test
+	public static int[] generatePositiveArray(int size, int value) {
+		int[] ans = new int[size];
+		for (int i = 0; i != size; i++) {
+			ans[i] = (int) (Math.random() * value) + 1;
+		}
+		return ans;
+	}
+
+	// for test
+	public static void printArray(int[] arr) {
+		for (int i = 0; i != arr.length; i++) {
+			System.out.print(arr[i] + " ");
+		}
+		System.out.println();
+	}
+
+	public static void main(String[] args) {
+		int len = 50;
+		int value = 100;
+		int testTime = 500000;
+		System.out.println("test begin");
+		for (int i = 0; i < testTime; i++) {
+			int[] arr = generatePositiveArray(len, value);
+			int K = (int) (Math.random() * value) + 1;
+			int ans1 = getMaxLength(arr, K);
+			int ans2 = right(arr, K);
+			if (ans1 != ans2) {
+				System.out.println("Oops!");
+				printArray(arr);
+				System.out.println("K : " + K);
+				System.out.println(ans1);
+				System.out.println(ans2);
+				break;
+			}
+		}
+		System.out.println("test end");
+	}
+
+}
diff --git a/src/class40/Code02_LongestSumSubArrayLength.java b/src/class40/Code02_LongestSumSubArrayLength.java
new file mode 100644
index 0000000..c1a21aa
--- /dev/null
+++ b/src/class40/Code02_LongestSumSubArrayLength.java
@@ -0,0 +1,90 @@
+package class40;
+
+import java.util.HashMap;
+
+public class Code02_LongestSumSubArrayLength {
+
+	public static int maxLength(int[] arr, int k) {
+		if (arr == null || arr.length == 0) {
+			return 0;
+		}
+		HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
+		map.put(0, -1); // important
+		int len = 0;
+		int sum = 0;
+		for (int i = 0; i < arr.length; i++) {
+			sum += arr[i];
+			if (map.containsKey(sum - k)) {
+				len = Math.max(i - map.get(sum - k), len);
+			}
+			if (!map.containsKey(sum)) {
+				map.put(sum, i);
+			}
+		}
+		return len;
+	}
+
+	// for test
+	public static int right(int[] arr, int K) {
+		int max = 0;
+		for (int i = 0; i < arr.length; i++) {
+			for (int j = i; j < arr.length; j++) {
+				if (valid(arr, i, j, K)) {
+					max = Math.max(max, j - i + 1);
+				}
+			}
+		}
+		return max;
+	}
+
+	// for test
+	public static boolean valid(int[] arr, int L, int R, int K) {
+		int sum = 0;
+		for (int i = L; i <= R; i++) {
+			sum += arr[i];
+		}
+		return sum == K;
+	}
+
+	// for test
+	public static int[] generateRandomArray(int size, int value) {
+		int[] ans = new int[(int) (Math.random() * size) + 1];
+		for (int i = 0; i < ans.length; i++) {
+			ans[i] = (int) (Math.random() * value) - (int) (Math.random() * value);
+		}
+		return ans;
+	}
+
+	// for test
+	public static void printArray(int[] arr) {
+		for (int i = 0; i != arr.length; i++) {
+			System.out.print(arr[i] + " ");
+		}
+		System.out.println();
+	}
+
+	public static void main(String[] args) {
+		int len = 50;
+		int value = 100;
+		int testTime = 500000;
+
+		System.out.println("test begin");
+		for (int i = 0; i < testTime; i++) {
+			int[] arr = generateRandomArray(len, value);
+			int K = (int) (Math.random() * value) - (int) (Math.random() * value);
+			int ans1 = maxLength(arr, K);
+			int ans2 = right(arr, K);
+			if (ans1 != ans2) {
+				System.out.println("Oops!");
+				printArray(arr);
+				System.out.println("K : " + K);
+				System.out.println(ans1);
+				System.out.println(ans2);
+				break;
+			}
+		}
+		System.out.println("test end");
+
+	}
+
+}
diff --git a/src/class40/Code03_LongestLessSumSubArrayLength.java b/src/class40/Code03_LongestLessSumSubArrayLength.java
new file mode 100644
index 0000000..5349d2b
--- /dev/null
+++ b/src/class40/Code03_LongestLessSumSubArrayLength.java
@@ -0,0 +1,105 @@
+package class40;
+
+public class Code03_LongestLessSumSubArrayLength {
+
+	public static int maxLengthAwesome(int[] arr, int k) {
+		if (arr == null || arr.length == 0) {
+			return 0;
+		}
+		int[] minSums = new int[arr.length];
+		int[] minSumEnds = new int[arr.length];
+		minSums[arr.length - 1] = arr[arr.length - 1];
+		minSumEnds[arr.length - 1] = arr.length - 1;
+		for (int i = arr.length - 2; i >= 0; i--) {
+			if (minSums[i + 1] < 0) {
+				minSums[i] = arr[i] + minSums[i + 1];
+				minSumEnds[i] = minSumEnds[i + 1];
+			} else {
+				minSums[i] = arr[i];
+				minSumEnds[i] = i;
+			}
+		}
+		int end = 0;
+		int sum = 0;
+		int res = 0;
+		// i是窗口的最左的位置，end扩出来的最右有效块儿的最后一个位置的，再下一个位置
+		// end也是下一块儿的开始位置
+		// 窗口：[i~end)
+		for (int i = 0; i < arr.length; i++) {
+			// while循环结束之后：
+			// 1) 如果以i开头的情况下，累加和<=k的最长子数组是arr[i..end-1]，看看这个子数组长度能不能更新res；
+			// 2) 如果以i开头的情况下，累加和<=k的最长子数组比arr[i..end-1]短，更新还是不更新res都不会影响最终结果；
+			while (end < arr.length && sum + minSums[end] <= k) {
+				sum += minSums[end];
+				end = minSumEnds[end] + 1;
+			}
+			res = Math.max(res, end - i);
+			if (end > i) { // 窗口内还有数 [i~end) [4,4)
+				sum -= arr[i];
+			} else { // 窗口内已经没有数了，说明从i开头的所有子数组累加和都不可能<=k
+				end = i + 1;
+			}
+		}
+		return res;
+	}
+
+	public static int maxLength(int[] arr, int k) {
+		int[] h = new int[arr.length + 1];
+		int sum = 0;
+		h[0] = sum;
+		for (int i = 0; i != arr.length; i++) {
+			sum += arr[i];
+			h[i + 1] = Math.max(sum, h[i]);
+		}
+		sum = 0;
+		int res = 0;
+		int pre = 0;
+		int len = 0;
+		for (int i = 0; i != arr.length; i++) {
+			sum += arr[i];
+			pre = getLessIndex(h, sum - k);
+			len = pre == -1 ? 0 : i - pre + 1;
+			res = Math.max(res, len);
+		}
+		return res;
+	}
+
+	public static int getLessIndex(int[] arr, int num) {
+		int low = 0;
+		int high = arr.length - 1;
+		int mid = 0;
+		int res = -1;
+		while (low <= high) {
+			mid = (low + high) / 2;
+			if (arr[mid] >= num) {
+				res = mid;
+				high = mid - 1;
+			} else {
+				low = mid + 1;
+			}
+		}
+		return res;
+	}
+
+	// for test
+	public static int[] generateRandomArray(int len, int maxValue) {
+		int[] res = new int[len];
+		for (int i = 0; i != res.length; i++) {
+			res[i] = (int) (Math.random() * maxValue) - (maxValue / 3);
+		}
+		return res;
+	}
+
+	public static void main(String[] args) {
+		System.out.println("test begin");
+		for (int i = 0; i < 10000000; i++) {
+			int[] arr = generateRandomArray(10, 20);
+			int k = (int) (Math.random() * 20) - 5;
+			if (maxLengthAwesome(arr, k) != maxLength(arr, k)) {
+				System.out.println("Oops!");
+			}
+		}
+		System.out.println("test finish");
+	}
+
+}
diff --git a/src/class40/Code04_AvgLessEqualValueLongestSubarray.java b/src/class40/Code04_AvgLessEqualValueLongestSubarray.java
new file mode 100644
index 0000000..c56eef9
--- /dev/null
+++ b/src/class40/Code04_AvgLessEqualValueLongestSubarray.java
@@ -0,0 +1,152 @@
+package class40;
+
+import java.util.TreeMap;
+
+public class Code04_AvgLessEqualValueLongestSubarray {
+
+	// 暴力解，时间复杂度O(N^3)，用于做对数器
+	public static int ways1(int[] arr, int v) {
+		int ans = 0;
+		for (int L = 0; L < arr.length; L++) {
+			for (int R = L; R < arr.length; R++) {
+				int sum = 0;
+				int k = R - L + 1;
+				for (int i = L; i <= R; i++) {
+					sum += arr[i];
+				}
+				double avg = (double) sum / (double) k;
+				if (avg <= v) {
+					ans = Math.max(ans, k);
+				}
+			}
+		}
+		return ans;
+	}
+
+	// 想实现的解法2，时间复杂度O(N*logN)
+	public static int ways2(int[] arr, int v) {
+		if (arr == null || arr.length == 0) {
+			return 0;
+		}
+		TreeMap<Integer, Integer> origins = new TreeMap<>();
+		int ans = 0;
+		int modify = 0;
+		for (int i = 0; i < arr.length; i++) {
+			int p1 = arr[i] <= v ? 1 : 0;
+			int p2 = 0;
+			int querry = -arr[i] - modify;
+			if (origins.floorKey(querry) != null) {
+				p2 = i - origins.get(origins.floorKey(querry)) + 1;
+			}
+			ans = Math.max(ans, Math.max(p1, p2));
+			int curOrigin = -modify - v;
+			if (origins.floorKey(curOrigin) == null) {
+				origins.put(curOrigin, i);
+			}
+			modify += arr[i] - v;
+		}
+		return ans;
+	}
+
+	// 想实现的解法3，时间复杂度O(N)
+	public static int ways3(int[] arr, int v) {
+		if (arr == null || arr.length == 0) {
+			return 0;
+		}
+		for (int i = 0; i < arr.length; i++) {
+			arr[i] -= v;
+		}
+		return maxLengthAwesome(arr, 0);
+	}
+
+	// 找到数组中累加和<=k的最长子数组
+	public static int maxLengthAwesome(int[] arr, int k) {
+		int N = arr.length;
+		int[] sums = new int[N];
+		int[] ends = new int[N];
+		sums[N - 1] = arr[N - 1];
+		ends[N - 1] = N - 1;
+		for (int i = N - 2; i >= 0; i--) {
+			if (sums[i + 1] < 0) {
+				sums[i] = arr[i] + sums[i + 1];
+				ends[i] = ends[i + 1];
+			} else {
+				sums[i] = arr[i];
+				ends[i] = i;
+			}
+		}
+		int end = 0;
+		int sum = 0;
+		int res = 0;
+		for (int i = 0; i < N; i++) {
+			while (end < N && sum + sums[end] <= k) {
+				sum += sums[end];
+				end = ends[end] + 1;
+			}
+			res = Math.max(res, end - i);
+			if (end > i) {
+				sum -= arr[i];
+			} else {
+				end = i + 1;
+			}
+		}
+		return res;
+	}
+
+	// 用于测试
+	public static int[] randomArray(int maxLen, int maxValue) {
+		int len = (int) (Math.random() * maxLen) + 1;
+		int[] ans = new int[len];
+		for (int i = 0; i < len; i++) {
+			ans[i] = (int) (Math.random() * maxValue);
+		}
+		return ans;
+	}
+
+	// 用于测试
+	public static int[] copyArray(int[] arr) {
+		int[] ans = new int[arr.length];
+		for (int i = 0; i < arr.length; i++) {
+			ans[i] = arr[i];
+		}
+		return ans;
+	}
+
+	// 用于测试
+	public static void printArray(int[] arr) {
+		for (int i = 0; i < arr.length; i++) {
+			System.out.print(arr[i] + " ");
+		}
+		System.out.println();
+	}
+
+	// 用于测试
+	public static void main(String[] args) {
+		System.out.println("测试开始");
+		int maxLen = 20;
+		int maxValue = 100;
+		int testTime = 500000;
+		for (int i = 0; i < testTime; i++) {
+			int[] arr = randomArray(maxLen, maxValue);
+			int value = (int) (Math.random() * maxValue);
+			int[] arr1 = copyArray(arr);
+			int[] arr2 = copyArray(arr);
+			int[] arr3 = copyArray(arr);
+			int ans1 = ways1(arr1, value);
+			int ans2 = ways2(arr2, value);
+			int ans3 = ways3(arr3, value);
+			if (ans1 != ans2 || ans1 != ans3) {
+				System.out.println("测试出错！");
+				System.out.print("测试数组：");
+				printArray(arr);
+				System.out.println("子数组平均值不小于 ：" + value);
+				System.out.println("方法1得到的最大长度：" + ans1);
+				System.out.println("方法2得到的最大长度：" + ans2);
+				System.out.println("方法3得到的最大长度：" + ans3);
+				System.out.println("=========================");
+			}
+		}
+		System.out.println("测试结束");
+	}
+
+}
diff --git a/src/class41/Code01_NiuNiuSplitField.java b/src/class41/Code01_NiuNiuSplitField.java
new file mode 100644
index 0000000..d98b48e
--- /dev/null
+++ b/src/class41/Code01_NiuNiuSplitField.java
@@ -0,0 +1,179 @@
+package class41;
+
+import java.util.*;
+
+public class Code01_NiuNiuSplitField {
+
+	// arr都是正数，0~i切的时候，怎么切最优，最优的结论生成一个数组返回
+	public static int[] getAnswers(int[] arr) {
+		if (arr == null || arr.length < 1) {
+			return null;
+		}
+		// ans[i] 代表的含义：
+		// arr[0..i]切两块的各种方案中，哪一种方案能让左右两部份的累加和最小值，尽量大
+		int[] ans = new int[arr.length];
+		ans[0] = 0;
+		int best = 0;// 左 0..0 右 无
+		for (int i = 1; i < arr.length; i++) {
+			while (best < i - 1 && getSplit(arr, best, i) < getSplit(arr, best + 1, i)) {
+				best++;
+			}
+			ans[i] = getSplit(arr, best, i);
+		}
+		return ans;
+	}
+
+	public static int getSum(int[] arr, int i, int j) {
+		return 0;
+	}
+
+	// arr[0..j] 如果我把切的这一刀定在m位置，左0..m，右m+1..j
+	public static int getSplit(int[] arr, int m, int j) {
+		return 0;
+	}
+
+	public static int maxMinSumIn16(int[][] matrix) {
+		if (matrix == null || matrix.length < 4 || matrix[0].length < 4) {
+			return 0;
+		}
+		// help[i][j] 含义，左上角为(0,0) 右下角为(i,j)的子矩阵累加和是多少
+		int[][] help = generateSumRecord(matrix);
+		// 通过help，得到任何子矩阵的累加和
+		int col = matrix[0].length;
+		int res = Integer.MIN_VALUE;
+		// 3个for循环在暴力枚举纵向三刀
+		for (int c1 = 0; c1 < col - 3; c1++) {
+			for (int c2 = c1 + 1; c2 < col - 2; c2++) {
+				for (int c3 = c2 + 1; c3 < col - 1; c3++) {
+					// c1 c2 c3
+					res = Math.max(res, getBestDicision(help, c1, c2, c3));
+				}
+			}
+		}
+		return res;
+	}
+
+	// record[i][j] 左上角点0,0， 有效角点i、j , 该矩阵的累加和
+	public static int[][] generateSumRecord(int[][] matrix) {
+		int row = matrix.length;
+		int col = matrix[0].length;
+		int[][] record = new int[row][col];
+		record[0][0] = matrix[0][0];
+		for (int i = 1; i < row; i++) {
+			record[i][0] = record[i - 1][0] + matrix[i][0];
+		}
+		for (int j = 1; j < col; j++) {
+			record[0][j] = record[0][j - 1] + matrix[0][j];
+		}
+		for (int i = 1; i < row; i++) {
+			for (int j = 1; j < col; j++) {
+				record[i][j] = record[i][j - 1] + record[i - 1][j] - record[i - 1][j - 1] + matrix[i][j];
+			}
+		}
+		return record;
+	}
+
+	// 忘掉原来的矩阵，只使用help
+	// 竖着三刀固定，c1，c2，c3
+	// 所有横着切三刀的可能性中，那种切法能得到最好的结果，把结果返回
+	public static int getBestDicision(int[][] help, int c1, int c2, int c3) {
+		// 0～i 切一刀，出来八块，最优指标，up[i]
+		int[] up = getUpSplitArray(help, c1, c2, c3); // 0行~i行 切一刀，分8块，min max
+
+		// i ~ N-1 切一刀，出来八块，最优指标，down[i]
+		int[] down = getDownSplitArray(help, c1, c2, c3); // i~n-1 切一刀
+
+		int res = Integer.MIN_VALUE;
+		for (int mid = 1; mid < help.length - 2; mid++) {
+			res = Math.max(res, Math.min(up[mid], down[mid + 1]));
+		}
+		return res;
+	}
+
+	public static int value(int[][] record, int c1, int c2, int c3, int prow, int crow) {
+		int value1 = area(record, prow, 0, crow, c1);
+		int value2 = area(record, prow, c1 + 1, crow, c2);
+		int value3 = area(record, prow, c2 + 1, crow, c3);
+		int value4 = area(record, prow, c3 + 1, crow, record[0].length - 1);
+		return Math.min(Math.min(value1, value2), Math.min(value3, value4));
+	}
+
+	public static int area(int[][] record, int i1, int j1, int i2, int j2) {
+		int all = record[i2][j2];
+		int left = j1 > 0 ? record[i2][j1 - 1] : 0;
+		int up = i1 > 0 ? record[i1 - 1][j2] : 0;
+		int makeUp = (i1 > 0 && j1 > 0) ? record[i1 - 1][j1 - 1] : 0;
+		return all - left - up + makeUp;
+	}
+
+	public static int[] getUpSplitArray(int[][] record, int c1, int c2, int c3) {
+		int size = record.length;
+		int[] up = new int[size];
+		int split = 0;
+		up[1] = Math.min(value(record, c1, c2, c3, 0, 0), value(record, c1, c2, c3, 1, 1));
+		for (int i = 2; i < size; i++) {
+			int minsMax = towSubMatrixMin(record, c1, c2, c3, 0, split, i);
+			while (split < i) {
+				if (split == i - 1) {
+					break;
+				}
+				int moved = towSubMatrixMin(record, c1, c2, c3, 0, split + 1, i);
+				if (moved < minsMax) {
+					break;
+				} else {
+					minsMax = moved;
+					split++;
+				}
+			}
+			up[i] = minsMax;
+		}
+		return up;
+	}
+
+	public static int[] getDownSplitArray(int[][] record, int c1, int c2, int c3) {
+		int size = record.length;
+		int[] down = new int[size];
+		int split = size - 1;
+		down[size - 2] = Math.min(value(record, c1, c2, c3, size - 2, size - 2),
+				value(record, c1, c2, c3, size - 1, size - 1));
+		for (int i = size - 3; i >= 0; i--) {
+			int minsMax = towSubMatrixMin(record, c1, c2, c3, i, split - 1, size - 1);
+			while (split > i) {
+				if (split == i + 1) {
+					break;
+				}
+				int moved = towSubMatrixMin(record, c1, c2, c3, i, split - 2, size - 1);
+				if (moved < minsMax) {
+					break;
+				} else {
+					minsMax = moved;
+					split--;
+				}
+			}
+			down[i] = minsMax;
+		}
+		return down;
+	}
+
+	public static int towSubMatrixMin(int[][] record, int c1, int c2, int c3, int i, int split, int j) {
+		return Math.min(value(record, c1, c2, c3, i, split), value(record, c1, c2, c3, split + 1, j));
+	}
+
+	public static void main(String[] args) {
+		Scanner in = new Scanner(System.in);
+		while (in.hasNext()) {
+			int n = in.nextInt();
+			int m = in.nextInt();
+			int[][] matrix = new int[n][m];
+			for (int i = 0; i < n; i++) {
+				char[] chas = in.next().toCharArray();
+				for (int j = 0; j < m; j++) {
+					matrix[i][j] = chas[j] - '0';
+				}
+			}
+			System.out.println(maxMinSumIn16(matrix));
+		}
+		in.close();
+	}
+
+}
\ No newline at end of file
diff --git a/src/class41/Code02_SplitArrayLargestSum.java b/src/class41/Code02_SplitArrayLargestSum.java
new file mode 100644
index 0000000..0de1cea
--- /dev/null
+++ b/src/class41/Code02_SplitArrayLargestSum.java
@@ -0,0 +1,124 @@
+package class41;
+
+public class Code02_SplitArrayLargestSum {
+
+	public static int splitArray1(int[] nums, int m) {
+		return process(nums, 0, m);
+	}
+
+	public static int process(int[] arr, int index, int part) {
+		if (index == arr.length) {
+			return 0;
+		}
+		if (part == 0) {
+			return -1;
+		}
+		int first = 0;
+		int min = Integer.MAX_VALUE;
+		for (int end = index; arr.length - end >= part; end++) {
+			first += arr[end];
+			int next = process(arr, end + 1, part - 1);
+			if (next != -1) {
+				min = Math.min(min, Math.max(first, next));
+			}
+		}
+		return min;
+	}
+
+	public static int splitArray2(int[] nums, int M) {
+		int N = nums.length;
+		int[] help = new int[nums.length + 1];
+		for (int i = 0; i < N; i++) {
+			help[i + 1] = help[i] + nums[i];
+		}
+		int[][] dp = new int[N][M + 1];
+		for (int i = 0; i < N; i++) {
+			dp[i][1] = help[i + 1] - help[0];
+		}
+		for (int i = 1; i < Math.min(N, M); i++) {
+			dp[i][i + 1] = Math.max(dp[i - 1][i], nums[i]);
+		}
+		for (int i = 2; i < N; i++) {
+			for (int j = 2; j <= Math.min(i, M); j++) {
+				dp[i][j] = Integer.MAX_VALUE;
+				for (int k = i; k >= j - 1; k--) {
+					dp[i][j] = Math.min(dp[i][j], Math.max(dp[k - 1][j - 1], help[i + 1] - help[k]));
+				}
+			}
+		}
+		return dp[N - 1][M];
+	}
+
+	public static int splitArray3(int[] nums, int M) {
+		int N = nums.length;
+		int[] help = new int[nums.length + 1];
+		for (int i = 0; i < N; i++) {
+			help[i + 1] = help[i] + nums[i];
+		}
+		int[][] dp = new int[N][M + 1];
+		int[][] best = new int[N][M + 1];
+		for (int i = 0; i < N; i++) {
+			dp[i][1] = help[i + 1] - help[0];
+		}
+		for (int i = 1; i < Math.min(N, M); i++) {
+			dp[i][i + 1] = Math.max(dp[i - 1][i], nums[i]);
+			best[i][i + 1] = i;
+		}
+		for (int i = 2; i < N; i++) {
+			for (int j = Math.min(i, M); j >= 2; j--) {
+				dp[i][j] = Integer.MAX_VALUE;
+				int left = best[i - 1][j];
+				int right = j + 1 > M ? i : best[i][j + 1];
+				for (int k = left; k <= right; k++) {
+					int curAns = Math.max(dp[k - 1][j - 1], help[i + 1] - help[k]);
+					if (dp[i][j] > curAns) {
+						dp[i][j] = curAns;
+						best[i][j] = k;
+					}
+				}
+			}
+		}
+		return dp[N - 1][M];
+	}
+
+	public static int splitArray4(int[] nums, int M) {
+		long sum = 0;
+		for (int i = 0; i < nums.length; i++) {
+			sum += nums[i];
+		}
+		long l = 0;
+		long r = sum;
+		long ans = 0;
+		while (l <= r) {
+			long mid = (l + r) / 2;
+			long cur = getNeedParts(nums, mid);
+			if (cur <= M) {
+				ans = mid;
+				r = mid - 1;
+			} else {
+				l = mid + 1;
+			}
+		}
+		return (int) ans;
+	}
+
+	public static int getNeedParts(int[] arr, long aim) {
+		for (int i = 0; i < arr.length; i++) {
+			if (arr[i] > aim) {
+				return Integer.MAX_VALUE;
+			}
+		}
+		int parts = 1;
+		int all = arr[0];
+		for (int i = 1; i < arr.length; i++) {
+			if (all + arr[i] > aim) {
+				parts++;
+				all = arr[i];
+			} else {
+				all += arr[i];
+			}
+		}
+		return parts;
+	}
+
+}
diff --git a/src/class42/Code01_ThrowChessPiecesProblem.java b/src/class42/Code01_ThrowChessPiecesProblem.java
new file mode 100644
index 0000000..2aa44ff
--- /dev/null
+++ b/src/class42/Code01_ThrowChessPiecesProblem.java
@@ -0,0 +1,194 @@
+package class42;
+
+public class Code01_ThrowChessPiecesProblem {
+
+	public static int solution1(int nLevel, int kChess) {
+		if (nLevel < 1 || kChess < 1) {
+			return 0;
+		}
+		return Process1(nLevel, kChess);
+	}
+
+	// rest还剩多少层楼需要去验证
+	// k还有多少颗棋子能够使用
+	// 一定要验证出最高的不会碎的楼层！但是每次都是坏运气。
+	// 返回至少需要扔几次？
+	public static int Process1(int rest, int k) {
+		if (rest == 0) {
+			return 0;
+		}
+		if (k == 1) {
+			return rest;
+		}
+		int min = Integer.MAX_VALUE;
+		for (int i = 1; i != rest + 1; i++) { // 第一次扔的时候，仍在了i层
+			min = Math.min(min,
+					Math.max(Process1(i - 1, k - 1), Process1(rest - i, k)));
+		}
+		return min + 1;
+	}
+
+	public static int solution2(int nLevel, int kChess) {
+		if (nLevel < 1 || kChess < 1) {
+			return 0;
+		}
+		if (kChess == 1) {
+			return nLevel;
+		}
+		int[][] dp = new int[nLevel + 1][kChess + 1];
+		for (int i = 1; i != dp.length; i++) {
+			dp[i][1] = i;
+		}
+		for (int i = 1; i != dp.length; i++) {
+			for (int j = 2; j != dp[0].length; j++) {
+				int min = Integer.MAX_VALUE;
+				for (int k = 1; k != i + 1; k++) {
+					min = Math.min(min, Math.max(dp[k - 1][j - 1], dp[i - k][j]));
+				}
+				dp[i][j] = min + 1;
+			}
+		}
+		return dp[nLevel][kChess];
+	}
+
+	public static int solution3(int nLevel, int kChess) {
+		if (nLevel < 1 || kChess < 1) {
+			return 0;
+		}
+		if (kChess == 1) {
+			return nLevel;
+		}
+		int[] preArr = new int[nLevel + 1];
+		int[] curArr = new int[nLevel + 1];
+		for (int i = 1; i != curArr.length; i++) {
+			curArr[i] = i;
+		}
+		for (int i = 1; i != kChess; i++) {
+			int[] tmp = preArr;
+			preArr = curArr;
+			curArr = tmp;
+			for (int j = 1; j != curArr.length; j++) {
+				int min = Integer.MAX_VALUE;
+				for (int k = 1; k != j + 1; k++) {
+					min = Math.min(min, Math.max(preArr[k - 1], curArr[j - k]));
+				}
+				curArr[j] = min + 1;
+			}
+		}
+		return curArr[curArr.length - 1];
+	}
+
+	public static int solution4(int nLevel, int kChess) {
+		if (nLevel < 1 || kChess < 1) {
+			return 0;
+		}
+		if (kChess == 1) {
+			return nLevel;
+		}
+		int[][] dp = new int[nLevel + 1][kChess + 1];
+		for (int i = 1; i != dp.length; i++) {
+			dp[i][1] = i;
+		}
+		int[] cands = new int[kChess + 1];
+		for (int i = 1; i != dp[0].length; i++) {
+			dp[1][i] = 1;
+			cands[i] = 1;
+		}
+		for (int i = 2; i < nLevel + 1; i++) {
+			for (int j = kChess; j > 1; j--) {
+				int min = Integer.MAX_VALUE;
+				int minEnum = cands[j];
+				int maxEnum = j == kChess ? i / 2 + 1 : cands[j + 1];
+				for (int k = minEnum; k < maxEnum + 1; k++) {
+					int cur = Math.max(dp[k - 1][j - 1], dp[i - k][j]);
+					if (cur <= min) {
+						min = cur;
+						cands[j] = k;
+					}
+				}
+				dp[i][j] = min + 1;
+			}
+		}
+		return dp[nLevel][kChess];
+	}
+
+	public static int solution5(int nLevel, int kChess) {
+		if (nLevel < 1 || kChess < 1) {
+			return 0;
+		}
+		int bsTimes = log2N(nLevel) + 1;
+		if (kChess >= bsTimes) {
+			return bsTimes;
+		}
+		int[] dp = new int[kChess];
+		int res = 0;
+		while (true) {
+			res++;
+			int previous = 0;
+			for (int i = 0; i < dp.length; i++) {
+				int tmp = dp[i];
+				dp[i] = dp[i] + previous + 1;
+				previous = tmp;
+				if (dp[i] >= nLevel) {
+					return res;
+				}
+			}
+		}
+	}
+
+	public static int log2N(int n) {
+		int res = -1;
+		while (n != 0) {
+			res++;
+			n >>>= 1;
+		}
+		return res;
+	}
+
+	public static void main(String[] args) {
+		System.out.println(solution1(21, 2));
+		System.out.println(solution2(21, 2));
+		System.out.println(solution3(21, 2));
+		System.out.println(solution4(21, 2));
+		System.out.println(solution5(21, 2));
+
+		System.out.println("==============");
+
+		System.out.println(solution2(105, 2));
+		System.out.println(solution3(105, 2));
+		System.out.println(solution4(105, 2));
+		System.out.println(solution5(105, 2));
+
+		System.out.println("==============");
+
+		System.out.println(solution2(3000, 10));
+		System.out.println(solution3(3000, 10));
+		System.out.println(solution4(3000, 10));
+		System.out.println(solution5(3000, 10));
+
+		System.out.println("==============");
+
+		System.out.println(solution2(6884, 5));
+		System.out.println(solution3(6884, 5));
+		System.out.println(solution4(6884, 5));
+		System.out.println(solution5(6884, 5));
+
+		System.out.println("==============");
+
+		System.out.println(solution2(6885, 5));
+		System.out.println(solution3(6885, 5));
+		System.out.println(solution4(6885, 5));
+		System.out.println(solution5(6885, 5));
+
+		System.out.println("==============");
+
+		int nLevel = 100000000;
+		int kChess = 10;
+		long start = System.currentTimeMillis();
+		System.out.println(solution5(nLevel, kChess));
+		long end = System.currentTimeMillis();
+		System.out.println("cost time: " + (end - start) + " ms");
+
+	}
+
+}
diff --git a/src/class42/Code02_PostOfficeProblem.java b/src/class42/Code02_PostOfficeProblem.java
new file mode 100644
index 0000000..8f91c03
--- /dev/null
+++ b/src/class42/Code02_PostOfficeProblem.java
@@ -0,0 +1,215 @@
+package class42;
+
+import java.util.Arrays;
+
+public class Code02_PostOfficeProblem {
+
+	public static int minDis1(int[] arr, int num) {
+		if (arr == null || arr.length < 2 || num < 1) {
+			return 0;
+		}
+		// record[L][R]表示如果arr[L...R]上只建立一个邮局，总距离最小是多少？
+		int[][] record = getRecord(arr);
+		int N = arr.length;
+		int[][] dp = new int[N][num + 1];
+		// dp[...][0] 0个邮局的时候如何如何
+		// dp[0][...] 0
+		for (int i = 0; i < N; i++) {
+			// 0...i 1
+			dp[i][1] = record[0][i];
+		}
+		for (int i = 1; i < N; i++) {
+			for (int j = 2; j <= Math.min(num, i); j++) {
+				// dp[i][j]
+				// 枚举最后一个邮局负责的范围，K...i
+				// i..i
+				// i-1..i
+				// i-2..i
+				// 1....i
+				// 0....i 单列
+				// 0...k-1 j-1个邮局 +
+				dp[i][j] = record[0][i];
+				for (int k = i; k > 0; k--) { // 1 .... i
+					dp[i][j] = Math.min(dp[i][j], dp[k - 1][j - 1] + record[k][i]);
+				}
+			}
+		}
+		return dp[N - 1][num];
+	}
+
+	public static int minDis2(int[] arr, int num) {
+		if (arr == null || arr.length < 2 || num < 1) {
+			return 0;
+		}
+		// record[L][R]表示如果arr[L...R]上只建立一个邮局，总距离最小是多少？
+		int[][] record = getRecord(arr);
+		int N = arr.length;
+		int[][] dp = new int[N][num + 1];
+		// dp[...][0]
+		// dp[0][...] 0..0 0
+		// choose[0][..] 0
+		// choose[i][j] 当时在求dp[i][j]的时候，
+		// 最右的邮局，如果是在负责k...i这一段的时候，取得的最优解，请把choose[i][j] = k
+		int[][] choose = new int[N][num + 1];
+		for (int i = 0; i < N; i++) {
+			// 0..i 1个邮局 0...i 0
+			dp[i][1] = record[0][i];
+		}
+		for (int i = 1; i < N; i++) {
+			for (int j = Math.min(num, i); j >= 2; j--) {
+				int down = choose[i - 1][j];
+				int up = j == Math.min(num, i) ? i : choose[i][j + 1];
+				dp[i][j] = record[0][i];
+				for (int k = Math.max(1, down); k <= Math.min(up, i); k++) {
+					if (dp[k - 1][j - 1] + record[k][i] < dp[i][j]) {
+						dp[i][j] = dp[k - 1][j - 1] + record[k][i];
+						choose[i][j] = k;
+					}
+				}
+			}
+		}
+		return dp[N - 1][num];
+	}
+
+	public static int[][] getRecord(int[] arr) {
+		int N = arr.length;
+		int[][] record = new int[N][N];
+		for (int L = 0; L < N; L++) {
+			for (int R = L + 1; R < N; R++) {
+				record[L][R] = record[L][R - 1] + arr[R] - arr[(L + R) >> 1];
+			}
+		}
+		return record;
+	}
+
+	public static int minDistances1(int[] arr, int num) {
+		if (arr == null || num < 1 || arr.length < num) {
+			return 0;
+		}
+		int[][] w = new int[arr.length + 1][arr.length + 1];
+		for (int i = 0; i < arr.length; i++) {
+			for (int j = i + 1; j < arr.length; j++) {
+				w[i][j] = w[i][j - 1] + arr[j] - arr[(i + j) / 2];
+			}
+		}
+		int[][] dp = new int[num][arr.length];
+		for (int j = 0; j != arr.length; j++) {
+			dp[0][j] = w[0][j];
+		}
+		for (int i = 1; i < num; i++) {
+			for (int j = i + 1; j < arr.length; j++) {
+				dp[i][j] = Integer.MAX_VALUE;
+				for (int k = 0; k <= j; k++) {
+					dp[i][j] = Math.min(dp[i][j], dp[i - 1][k] + w[k + 1][j]);
+				}
+			}
+		}
+		return dp[num - 1][arr.length - 1];
+	}
+
+	public static int minDistances2(int[] arr, int num) {
+		if (arr == null || num < 1 || arr.length < num) {
+			return 0;
+		}
+		int[][] w = new int[arr.length + 1][arr.length + 1];
+		for (int i = 0; i < arr.length; i++) {
+			for (int j = i + 1; j < arr.length; j++) {
+				w[i][j] = w[i][j - 1] + arr[j] - arr[(i + j) / 2];
+			}
+		}
+		int[][] dp = new int[num][arr.length];
+		int[][] s = new int[num][arr.length];
+		for (int j = 0; j != arr.length; j++) {
+			dp[0][j] = w[0][j];
+			s[0][j] = 0;
+		}
+		int minK = 0;
+		int maxK = 0;
+		int cur = 0;
+		for (int i = 1; i < num; i++) {
+			for (int j = arr.length - 1; j > i; j--) {
+				minK = s[i - 1][j];
+				maxK = j == arr.length - 1 ? arr.length - 1 : s[i][j + 1];
+				dp[i][j] = Integer.MAX_VALUE;
+				for (int k = minK; k <= maxK; k++) {
+					cur = dp[i - 1][k] + w[k + 1][j];
+					if (cur <= dp[i][j]) {
+						dp[i][j] = cur;
+						s[i][j] = k;
+					}
+				}
+			}
+		}
+		return dp[num - 1][arr.length - 1];
+	}
+
+	// for test
+	public static int[] getSortedArray(int len, int range) {
+		int[] arr = new int[len];
+		for (int i = 0; i != len; i++) {
+			arr[i] = (int) (Math.random() * range);
+		}
+		Arrays.sort(arr);
+		return arr;
+	}
+
+	// for test
+	public static void printArray(int[] arr) {
+		for (int i = 0; i != arr.length; i++) {
+			System.out.print(arr[i] + " ");
+		}
+		System.out.println();
+	}
+
+	// for test
+	public static void main(String[] args) {
+		int[] arr = { 1,3,8,10,12 };
+		int num = 3;
+		System.out.println(minDis1(arr, num));
+		System.out.println(minDistances1(arr, num));
+		System.out.println(minDistances2(arr, num));
+
+		int times = 100; // test time
+		int len = 1000; // test array length
+		int range = 2000; // every number in [0,range)
+		int p = 50; // post office number max
+		long time1 = 0; // method1 all run time
+		long time2 = 0;// method2 all run time
+		long time3 = 0;
+		long start = 0;
+		long end = 0;
+		int res1 = 0;
+		int res2 = 0;
+		int res3 = 0;
+		for (int i = 0; i != times; i++) {
+			int office = (int) (Math.random() * p) + 1;
+			arr = getSortedArray(len, range);
+			start = System.currentTimeMillis();
+			res1 = minDistances1(arr, office);
+			end = System.currentTimeMillis();
+			time1 += end - start;
+			start = System.currentTimeMillis();
+			res2 = minDis2(arr, office);
+			end = System.currentTimeMillis();
+			time2 += end - start;
+
+			start = System.currentTimeMillis();
+			res3 = minDis1(arr, office);
+			end = System.currentTimeMillis();
+			time3 += end - start;
+			if (res1 != res2 || res1 != res3) {
+				printArray(arr);
+				break;
+			}
+			if (i % 10 == 0) {
+				System.out.print(". ");
+			}
+		}
+		System.out.println();
+		System.out.println("method1 all run time(ms): " + time1);
+		System.out.println("method2 all run time(ms): " + time2);
+		System.out.println("method3 all run time(ms): " + time3);
+
+	}
+
+}
diff --git a/src/class43/Code01_TSP.java b/src/class43/Code01_TSP.java
new file mode 100644
index 0000000..87bd69c
--- /dev/null
+++ b/src/class43/Code01_TSP.java
@@ -0,0 +1,295 @@
+package class43;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Code01_TSP {
+
+	public static int t1(int[][] matrix) {
+		int N = matrix.length; // 0...N-1
+		// set
+		// set.get(i) != null i这座城市在集合里
+		// set.get(i) == null i这座城市不在集合里
+		List<Integer> set = new ArrayList<>();
+		for (int i = 0; i < N; i++) {
+			set.add(1);
+		}
+		return func1(matrix, set, 0);
+	}
+
+	// 任何两座城市之间的距离，可以在matrix里面拿到
+	// set中表示着哪些城市的集合，
+	// start这座城一定在set里，
+	// 从start出发，要把set中所有的城市过一遍，最终回到0这座城市，最小距离是多少
+	public static int func1(int[][] matrix, List<Integer> set, int start) {
+		int cityNum = 0;
+		for (int i = 0; i < set.size(); i++) {
+			if (set.get(i) != null) {
+				cityNum++;
+			}
+		}
+		if (cityNum == 1) {
+			return matrix[start][0];
+		}
+		// 不只start这一座城
+		set.set(start, null);
+		int min = Integer.MAX_VALUE;
+		for (int i = 0; i < set.size(); i++) {
+			if (set.get(i) != null && i != start) {
+				// start -> i i... -> 0
+				int cur = matrix[start][i] + func1(matrix, set, i);
+				min = Math.min(min, cur);
+			}
+		}
+		set.set(start, 1);
+		return min;
+	}
+
+	public static int t2(int[][] matrix) {
+		int N = matrix.length; // 0...N-1
+		// 7座城 1111111
+		int allCity = (1 << N) - 1;
+		return f2(matrix, allCity, 0);
+	}
+
+	// 任何两座城市之间的距离，可以在matrix里面拿到
+	// set中表示着哪些城市的集合，
+	// start这座城一定在set里，
+	// 从start出发，要把set中所有的城市过一遍，最终回到0这座城市，最小距离是多少
+	public static int f2(int[][] matrix, int cityStatus, int start) {
+		// cityStatus == cityStatux & (~cityStaus + 1)
+
+		if (cityStatus == (cityStatus & (~cityStatus + 1))) {
+			return matrix[start][0];
+		}
+
+		// 把start位的1去掉，
+		cityStatus &= (~(1 << start));
+		int min = Integer.MAX_VALUE;
+		// 枚举所有的城市
+		for (int move = 0; move < matrix.length; move++) {
+			if (move != start && (cityStatus & (1 << move)) != 0) {
+				int cur = matrix[start][move] + f2(matrix, cityStatus, move);
+				min = Math.min(min, cur);
+			}
+		}
+		cityStatus |= (1 << start);
+		return min;
+	}
+
+	public static int t3(int[][] matrix) {
+		int N = matrix.length; // 0...N-1
+		// 7座城 1111111
+		int allCity = (1 << N) - 1;
+		int[][] dp = new int[1 << N][N];
+		for (int i = 0; i < (1 << N); i++) {
+			for (int j = 0; j < N; j++) {
+				dp[i][j] = -1;
+			}
+		}
+		return f3(matrix, allCity, 0, dp);
+	}
+
+	// 任何两座城市之间的距离，可以在matrix里面拿到
+	// set中表示着哪些城市的集合，
+	// start这座城一定在set里，
+	// 从start出发，要把set中所有的城市过一遍，最终回到0这座城市，最小距离是多少
+	public static int f3(int[][] matrix, int cityStatus, int start, int[][] dp) {
+		if (dp[cityStatus][start] != -1) {
+			return dp[cityStatus][start];
+		}
+		if (cityStatus == (cityStatus & (~cityStatus + 1))) {
+			dp[cityStatus][start] = matrix[start][0];
+		} else {
+			// 把start位的1去掉，
+			cityStatus &= (~(1 << start));
+			int min = Integer.MAX_VALUE;
+			// 枚举所有的城市
+			for (int move = 0; move < matrix.length; move++) {
+				if (move != start && (cityStatus & (1 << move)) != 0) {
+					int cur = matrix[start][move] + f3(matrix, cityStatus, move, dp);
+					min = Math.min(min, cur);
+				}
+			}
+			cityStatus |= (1 << start);
+			dp[cityStatus][start] = min;
+		}
+		return dp[cityStatus][start];
+	}
+
+	public static int t4(int[][] matrix) {
+		int N = matrix.length; // 0...N-1
+		int statusNums = 1 << N;
+		int[][] dp = new int[statusNums][N];
+
+		for (int status = 0; status < statusNums; status++) {
+			for (int start = 0; start < N; start++) {
+				if ((status & (1 << start)) != 0) {
+					if (status == (status & (~status + 1))) {
+						dp[status][start] = matrix[start][0];
+					} else {
+						int min = Integer.MAX_VALUE;
+						// start 城市在status里去掉之后，的状态
+						int preStatus = status & (~(1 << start));
+						// start -> i
+						for (int i = 0; i < N; i++) {
+							if ((preStatus & (1 << i)) != 0) {
+								int cur = matrix[start][i] + dp[preStatus][i];
+								min = Math.min(min, cur);
+							}
+						}
+						dp[status][start] = min;
+					}
+				}
+			}
+		}
+		return dp[statusNums - 1][0];
+	}
+
+	// matrix[i][j] -> i城市到j城市的距离
+	public static int tsp1(int[][] matrix, int origin) {
+		if (matrix == null || matrix.length < 2 || origin < 0 || origin >= matrix.length) {
+			return 0;
+		}
+		// 要考虑的集合
+		ArrayList<Integer> cities = new ArrayList<>();
+		// cities[0] != null 表示0城在集合里
+		// cities[i] != null 表示i城在集合里
+		for (int i = 0; i < matrix.length; i++) {
+			cities.add(1);
+		}
+		// null,1,1,1,1,1,1
+		// origin城不参与集合
+		cities.set(origin, null);
+		return process(matrix, origin, cities, origin);
+	}
+
+	// matrix 所有距离，存在其中
+	// origin 固定参数，唯一的目标
+	// cities 要考虑的集合，一定不含有origin
+	// 当前来到的城市是谁，cur
+	public static int process(int[][] matrix, int aim, ArrayList<Integer> cities, int cur) {
+		boolean hasCity = false; // 集团中还是否有城市
+		int ans = Integer.MAX_VALUE;
+		for (int i = 0; i < cities.size(); i++) {
+			if (cities.get(i) != null) {
+				hasCity = true;
+				cities.set(i, null);
+				// matrix[cur][i] + f(i, 集团(去掉i) )
+				ans = Math.min(ans, matrix[cur][i] + process(matrix, aim, cities, i));
+				cities.set(i, 1);
+			}
+		}
+		return hasCity ? ans : matrix[cur][aim];
+	}
+
+	// cities 里，一定含有cur这座城
+	// 解决的是，集合从cur出发，通过集合里所有的城市，最终来到aim，最短距离
+	public static int process2(int[][] matrix, int aim, ArrayList<Integer> cities, int cur) {
+		if (cities.size() == 1) {
+			return matrix[cur][aim];
+		}
+		cities.set(cur, null);
+		int ans = Integer.MAX_VALUE;
+		for (int i = 0; i < cities.size(); i++) {
+			if (cities.get(i) != null) {
+				int dis = matrix[cur][i] + process2(matrix, aim, cities, i);
+				ans = Math.min(ans, dis);
+			}
+		}
+		cities.set(cur, 1);
+		return ans;
+	}
+
+	public static int tsp2(int[][] matrix, int origin) {
+		if (matrix == null || matrix.length < 2 || origin < 0 || origin >= matrix.length) {
+			return 0;
+		}
+		int N = matrix.length - 1; // 除去origin之后是n-1个点
+		int S = 1 << N; // 状态数量
+		int[][] dp = new int[S][N];
+		int icity = 0;
+		int kcity = 0;
+		for (int i = 0; i < N; i++) {
+			icity = i < origin ? i : i + 1;
+			// 00000000 i
+			dp[0][i] = matrix[icity][origin];
+		}
+		for (int status = 1; status < S; status++) {
+			// 尝试每一种状态 status = 0 0 1 0 0 0 0 0 0
+			// 下标 8 7 6 5 4 3 2 1 0
+			for (int i = 0; i < N; i++) {
+				// i 枚举的出发城市
+				dp[status][i] = Integer.MAX_VALUE;
+				if ((1 << i & status) != 0) {
+					// 如果i这座城是可以枚举的，i = 6 ， i对应的原始城的编号，icity
+					icity = i < origin ? i : i + 1;
+					for (int k = 0; k < N; k++) { // i 这一步连到的点，k
+						if ((1 << k & status) != 0) { // i 这一步可以连到k
+							kcity = k < origin ? k : k + 1; // k对应的原始城的编号，kcity
+							dp[status][i] = Math.min(dp[status][i], dp[status ^ (1 << i)][k] + matrix[icity][kcity]);
+						}
+					}
+				}
+			}
+		}
+		int ans = Integer.MAX_VALUE;
+		for (int i = 0; i < N; i++) {
+			icity = i < origin ? i : i + 1;
+			ans = Math.min(ans, dp[S - 1][i] + matrix[origin][icity]);
+		}
+		return ans;
+	}
+
+	public static int[][] generateGraph(int maxSize, int maxValue) {
+		int len = (int) (Math.random() * maxSize) + 1;
+		int[][] matrix = new int[len][len];
+		for (int i = 0; i < len; i++) {
+			for (int j = 0; j < len; j++) {
+				matrix[i][j] = (int) (Math.random() * maxValue) + 1;
+			}
+		}
+		for (int i = 0; i < len; i++) {
+			matrix[i][i] = 0;
+		}
+		return matrix;
+	}
+
+	public static void main(String[] args) {
+		int len = 10;
+		int value = 100;
+		System.out.println("功能测试开始");
+		for (int i = 0; i < 20000; i++) {
+			int[][] matrix = generateGraph(len, value);
+			int origin = (int) (Math.random() * matrix.length);
+			int ans1 = t3(matrix);
+			int ans2 = t4(matrix);
+			int ans3 = tsp2(matrix, origin);
+			if (ans1 != ans2 || ans1 != ans3) {
+				System.out.println("fuck");
+			}
+		}
+		System.out.println("功能测试结束");
+
+		len = 22;
+		System.out.println("性能测试开始，数据规模 : " + len);
+		int[][] matrix = new int[len][len];
+		for (int i = 0; i < len; i++) {
+			for (int j = 0; j < len; j++) {
+				matrix[i][j] = (int) (Math.random() * value) + 1;
+			}
+		}
+		for (int i = 0; i < len; i++) {
+			matrix[i][i] = 0;
+		}
+		long start;
+		long end;
+		start = System.currentTimeMillis();
+		t4(matrix);
+		end = System.currentTimeMillis();
+		System.out.println("运行时间 : " + (end - start) + " 毫秒");
+		System.out.println("性能测试结束");
+
+	}
+
+}
diff --git a/src/class43/Code02_PavingTile.java b/src/class43/Code02_PavingTile.java
new file mode 100644
index 0000000..18b3b6d
--- /dev/null
+++ b/src/class43/Code02_PavingTile.java
@@ -0,0 +1,131 @@
+package class43;
+
+public class Code02_PavingTile {
+
+	/*
+	 * 2*M铺地的问题非常简单，这个是解决N*M铺地的问题
+	 */
+
+	public static int ways1(int N, int M) {
+		if (N < 1 || M < 1 || ((N * M) & 1) != 0) {
+			return 0;
+		}
+		if (N == 1 || M == 1) {
+			return 1;
+		}
+		int[] pre = new int[M]; // pre代表-1行的状况
+		for (int i = 0; i < pre.length; i++) {
+			pre[i] = 1;
+		}
+		return process(pre, 0, N);
+	}
+
+	// pre 表示level-1行的状态
+	// level表示，正在level行做决定
+	// N 表示一共有多少行  固定的
+	// level-2行及其之上所有行，都摆满砖了
+	// level做决定，让所有区域都满，方法数返回s
+	public static int process(int[] pre, int level, int N) {
+		if (level == N) { // base case
+			for (int i = 0; i < pre.length; i++) {
+				if (pre[i] == 0) {
+					return 0;
+				}
+			}
+			return 1;
+		}
+		
+		// 没到终止行，可以选择在当前的level行摆瓷砖
+		int[] op = getOp(pre);
+		return dfs(op, 0, level, N);
+	}
+
+	// op[i] == 0 可以考虑摆砖
+	// op[i] == 1 只能竖着向上
+	public static int dfs(int[] op, int col, int level, int N) {
+		 // 在列上自由发挥，玩深度优先遍历，当col来到终止列，i行的决定做完了
+		// 轮到i+1行，做决定
+		if (col == op.length) {
+			return process(op, level + 1, N);
+		}
+		int ans = 0;
+		// col位置不横摆
+		ans += dfs(op, col + 1, level, N); // col位置上不摆横转
+		//  col位置横摆, 向右
+		if (col + 1 < op.length && op[col] == 0 && op[col + 1] == 0) {
+			op[col] = 1;
+			op[col + 1] = 1;
+			ans += dfs(op, col + 2, level, N);
+			op[col] = 0;
+			op[col + 1] = 0;
+		}
+		return ans;
+	}
+
+	public static int[] getOp(int[] pre) {
+		int[] cur = new int[pre.length];
+		for (int i = 0; i < pre.length; i++) {
+			cur[i] = pre[i] ^ 1;
+		}
+		return cur;
+	}
+
+	public static int ways2(int N, int M) {
+		if (N < 1 || M < 1 || ((N * M) & 1) != 0) {
+			return 0;
+		}
+		if (N == 1 || M == 1) {
+			return 1;
+		}
+		int big = N > M ? N : M;
+		int small = big == N ? M : N;
+		// big * small
+		int sn = 1 << small;
+		int limit = sn - 1; // 全满状态
+		int[] dp = new int[sn];
+		dp[limit] = 1; // -1行全是满的
+		// dp     -1 行的状况
+		// dp[0000] 0
+		// dp[0001] 0
+		// dp[1111] 1
+		int[] cur = new int[sn]; // 当前行, 要算出所有状态下的解
+		for (int level = 0; level < big; level++) {
+			for (int status = 0; status < sn; status++) {
+				if (dp[status] != 0) { // 状态出现了
+					// 0...1100
+					// 1...0011
+					// 0...1111
+					// 0...0011
+					int op = (~status) & limit;
+					dfs(dp[status], op, 0, small - 1, cur);
+				}
+			}
+			for (int i = 0; i < sn; i++) {
+				dp[i] = 0;
+			}
+			int[] tmp = dp;
+			dp = cur;
+			cur = tmp;
+		}
+		return dp[limit];
+	}
+
+	public static void dfs(int way, int op, int index, int end, int[] cur) {
+		if (index == end) {
+			cur[op] += way;
+		} else {
+			dfs(way, op, index + 1, end, cur);
+			if (((3 << index) & op) == 0) { // 11 << index  可以放砖
+				dfs(way, op | (3 << index), index + 1, end, cur);
+			}
+		}
+	}
+
+	public static void main(String[] args) {
+		int N = 8;
+		int M = 8;
+		System.out.println(ways1(N, M));
+		System.out.println(ways2(N, M));
+	}
+
+}
diff --git a/src/class43/Code03_CanIWin.java b/src/class43/Code03_CanIWin.java
new file mode 100644
index 0000000..c0221c7
--- /dev/null
+++ b/src/class43/Code03_CanIWin.java
@@ -0,0 +1,64 @@
+package class43;
+
+// leetcode 464题
+public class Code03_CanIWin {
+
+	// 这个是暴力尝试，思路是正确的，超时而已
+	public static boolean canIWin1(int choose, int total) {
+		if (total == 0) {
+			return true;
+		}
+		if ((choose * (choose + 1) >> 1) < total) {
+			return false;
+		}
+		return process1(choose, 0, total);
+	}
+
+	public static boolean process1(int choose, int status, int rest) {
+		if (rest <= 0) {
+			return false;
+		}
+		for (int i = 1; i <= choose; i++) {
+			if (((1 << i) & status) == 0) {
+				if (!process1(choose, (status | (1 << i)), rest - i)) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+	// 暴力尝试改动态规划而已
+	public static boolean canIWin2(int choose, int total) {
+		if (total == 0) {
+			return true;
+		}
+		if ((choose * (choose + 1) >> 1) < total) {
+			return false;
+		}
+		int[] dp = new int[1 << (choose + 1)];
+		return process2(choose, 0, total, dp);
+	}
+
+	// 为什么明明status和rest是两个可变参数，却只用status来代表状态(也就是dp)
+	// 因为选了一批数字之后，得到的和一定是一样的，所以rest是由status决定的，所以rest不需要参与记忆化搜索
+	public static boolean process2(int choose, int status, int rest, int[] dp) {
+		if (dp[status] != 0) {
+			return dp[status] == 1 ? true : false;
+		}
+		boolean ans = false;
+		if (rest > 0) {
+			for (int i = 1; i <= choose; i++) {
+				if (((1 << i) & status) == 0) {
+					if (!process2(choose, (status | (1 << i)), rest - i, dp)) {
+						ans = true;
+						break;
+					}
+				}
+			}
+		}
+		dp[status] = ans ? 1 : -1;
+		return ans;
+	}
+
+}
diff --git a/src/class44/Code01_CreateMaximumNumber.java b/src/class44/Code01_CreateMaximumNumber.java
new file mode 100644
index 0000000..bb5e182
--- /dev/null
+++ b/src/class44/Code01_CreateMaximumNumber.java
@@ -0,0 +1,248 @@
+package class44;
+
+// 测试链接: https://leetcode.com/problems/create-maximum-number/
+public class Code01_CreateMaximumNumber {
+
+	public static int[] maxNumber1(int[] nums1, int[] nums2, int k) {
+		int len1 = nums1.length;
+		int len2 = nums2.length;
+		if (k < 0 || k > len1 + len2) {
+			return null;
+		}
+		int[] res = new int[k];
+		int[][] dp1 = getdp(nums1); // 生成dp1这个表，以后从nums1中，只要固定拿N个数，
+		int[][] dp2 = getdp(nums2);
+		for (int get1 = Math.max(0, k - len2); get1 <= Math.min(k, len1); get1++) {
+			// arr1 挑 get1个，怎么得到一个最优结果
+			int[] pick1 = maxPick(nums1, dp1, get1);
+			int[] pick2 = maxPick(nums2, dp2, k - get1);
+			int[] merge = merge(pick1, pick2);
+			res = preMoreThanLast(res, 0, merge, 0) ? res : merge;
+		}
+		return res;
+	}
+
+	public static int[] merge(int[] nums1, int[] nums2) {
+		int k = nums1.length + nums2.length;
+		int[] ans = new int[k];
+		for (int i = 0, j = 0, r = 0; r < k; ++r) {
+			ans[r] = preMoreThanLast(nums1, i, nums2, j) ? nums1[i++] : nums2[j++];
+		}
+		return ans;
+	}
+
+	public static boolean preMoreThanLast(int[] nums1, int i, int[] nums2, int j) {
+		while (i < nums1.length && j < nums2.length && nums1[i] == nums2[j]) {
+			i++;
+			j++;
+		}
+		return j == nums2.length || (i < nums1.length && nums1[i] > nums2[j]);
+	}
+
+	public static int[] maxNumber2(int[] nums1, int[] nums2, int k) {
+		int len1 = nums1.length;
+		int len2 = nums2.length;
+		if (k < 0 || k > len1 + len2) {
+			return null;
+		}
+		int[] res = new int[k];
+		int[][] dp1 = getdp(nums1);
+		int[][] dp2 = getdp(nums2);
+		for (int get1 = Math.max(0, k - len2); get1 <= Math.min(k, len1); get1++) {
+			int[] pick1 = maxPick(nums1, dp1, get1);
+			int[] pick2 = maxPick(nums2, dp2, k - get1);
+			int[] merge = mergeBySuffixArray(pick1, pick2);
+			res = moreThan(res, merge) ? res : merge;
+		}
+		return res;
+	}
+
+	public static boolean moreThan(int[] pre, int[] last) {
+		int i = 0;
+		int j = 0;
+		while (i < pre.length && j < last.length && pre[i] == last[j]) {
+			i++;
+			j++;
+		}
+		return j == last.length || (i < pre.length && pre[i] > last[j]);
+	}
+
+	public static int[] mergeBySuffixArray(int[] nums1, int[] nums2) {
+		int size1 = nums1.length;
+		int size2 = nums2.length;
+		int[] nums = new int[size1 + 1 + size2];
+		for (int i = 0; i < size1; i++) {
+			nums[i] = nums1[i] + 2;
+		}
+		nums[size1] = 1;
+		for (int j = 0; j < size2; j++) {
+			nums[j + size1 + 1] = nums2[j] + 2;
+		}
+		DC3 dc3 = new DC3(nums, 11);
+		int[] rank = dc3.rank;
+		int[] ans = new int[size1 + size2];
+		int i = 0;
+		int j = 0;
+		int r = 0;
+		while (i < size1 && j < size2) {
+			ans[r++] = rank[i] > rank[j + size1 + 1] ? nums1[i++] : nums2[j++];
+		}
+		while (i < size1) {
+			ans[r++] = nums1[i++];
+		}
+		while (j < size2) {
+			ans[r++] = nums2[j++];
+		}
+		return ans;
+	}
+
+	public static class DC3 {
+
+		public int[] sa;
+		public int[] rank;
+
+		public DC3(int[] nums, int max) {
+			sa = sa(nums, max);
+			rank = rank();
+		}
+
+		private int[] sa(int[] nums, int max) {
+			int n = nums.length;
+			int[] arr = new int[n + 3];
+			for (int i = 0; i < n; i++) {
+				arr[i] = nums[i];
+			}
+			return skew(arr, n, max);
+		}
+
+		private int[] skew(int[] nums, int n, int K) {
+			int n0 = (n + 2) / 3, n1 = (n + 1) / 3, n2 = n / 3, n02 = n0 + n2;
+			int[] s12 = new int[n02 + 3], sa12 = new int[n02 + 3];
+			for (int i = 0, j = 0; i < n + (n0 - n1); ++i) {
+				if (0 != i % 3) {
+					s12[j++] = i;
+				}
+			}
+			radixPass(nums, s12, sa12, 2, n02, K);
+			radixPass(nums, sa12, s12, 1, n02, K);
+			radixPass(nums, s12, sa12, 0, n02, K);
+			int name = 0, c0 = -1, c1 = -1, c2 = -1;
+			for (int i = 0; i < n02; ++i) {
+				if (c0 != nums[sa12[i]] || c1 != nums[sa12[i] + 1] || c2 != nums[sa12[i] + 2]) {
+					name++;
+					c0 = nums[sa12[i]];
+					c1 = nums[sa12[i] + 1];
+					c2 = nums[sa12[i] + 2];
+				}
+				if (1 == sa12[i] % 3) {
+					s12[sa12[i] / 3] = name;
+				} else {
+					s12[sa12[i] / 3 + n0] = name;
+				}
+			}
+			if (name < n02) {
+				sa12 = skew(s12, n02, name);
+				for (int i = 0; i < n02; i++) {
+					s12[sa12[i]] = i + 1;
+				}
+			} else {
+				for (int i = 0; i < n02; i++) {
+					sa12[s12[i] - 1] = i;
+				}
+			}
+			int[] s0 = new int[n0], sa0 = new int[n0];
+			for (int i = 0, j = 0; i < n02; i++) {
+				if (sa12[i] < n0) {
+					s0[j++] = 3 * sa12[i];
+				}
+			}
+			radixPass(nums, s0, sa0, 0, n0, K);
+			int[] sa = new int[n];
+			for (int p = 0, t = n0 - n1, k = 0; k < n; k++) {
+				int i = sa12[t] < n0 ? sa12[t] * 3 + 1 : (sa12[t] - n0) * 3 + 2;
+				int j = sa0[p];
+				if (sa12[t] < n0 ? leq(nums[i], s12[sa12[t] + n0], nums[j], s12[j / 3])
+						: leq(nums[i], nums[i + 1], s12[sa12[t] - n0 + 1], nums[j], nums[j + 1], s12[j / 3 + n0])) {
+					sa[k] = i;
+					t++;
+					if (t == n02) {
+						for (k++; p < n0; p++, k++) {
+							sa[k] = sa0[p];
+						}
+					}
+				} else {
+					sa[k] = j;
+					p++;
+					if (p == n0) {
+						for (k++; t < n02; t++, k++) {
+							sa[k] = sa12[t] < n0 ? sa12[t] * 3 + 1 : (sa12[t] - n0) * 3 + 2;
+						}
+					}
+				}
+			}
+			return sa;
+		}
+
+		private void radixPass(int[] nums, int[] input, int[] output, int offset, int n, int k) {
+			int[] cnt = new int[k + 1];
+			for (int i = 0; i < n; ++i) {
+				cnt[nums[input[i] + offset]]++;
+			}
+			for (int i = 0, sum = 0; i < cnt.length; ++i) {
+				int t = cnt[i];
+				cnt[i] = sum;
+				sum += t;
+			}
+			for (int i = 0; i < n; ++i) {
+				output[cnt[nums[input[i] + offset]]++] = input[i];
+			}
+		}
+
+		private boolean leq(int a1, int a2, int b1, int b2) {
+			return a1 < b1 || (a1 == b1 && a2 <= b2);
+		}
+
+		private boolean leq(int a1, int a2, int a3, int b1, int b2, int b3) {
+			return a1 < b1 || (a1 == b1 && leq(a2, a3, b2, b3));
+		}
+
+		private int[] rank() {
+			int n = sa.length;
+			int[] ans = new int[n];
+			for (int i = 0; i < n; i++) {
+				ans[sa[i]] = i + 1;
+			}
+			return ans;
+		}
+
+	}
+
+	public static int[][] getdp(int[] arr) {
+		int size = arr.length; // 0~N-1
+		int pick = arr.length + 1; // 1 ~ N
+		int[][] dp = new int[size][pick];
+		// get 不从0开始，因为拿0个无意义
+		// get 1
+		for (int get = 1; get < pick; get++) { // 1 ~ N
+			int maxIndex = size - get;
+			// i~N-1
+			for (int i = size - get; i >= 0; i--) {
+				if (arr[i] >= arr[maxIndex]) {
+					maxIndex = i;
+				}
+				dp[i][get] = maxIndex;
+			}
+		}
+		return dp;
+	}
+
+	public static int[] maxPick(int[] arr, int[][] dp, int pick) {
+		int[] res = new int[pick];
+		for (int resIndex = 0, dpRow = 0; pick > 0; pick--, resIndex++) {
+			res[resIndex] = arr[dp[dpRow][pick]];
+			dpRow = dp[dpRow][pick] + 1;
+		}
+		return res;
+	}
+
+}
diff --git a/src/class44/Code02_LastSubstringInLexicographicalOrder.java b/src/class44/Code02_LastSubstringInLexicographicalOrder.java
new file mode 100644
index 0000000..186fb06
--- /dev/null
+++ b/src/class44/Code02_LastSubstringInLexicographicalOrder.java
@@ -0,0 +1,148 @@
+package class44;
+
+// 测试链接: https://leetcode.com/problems/last-substring-in-lexicographical-order/
+public class Code02_LastSubstringInLexicographicalOrder {
+
+	public static String lastSubstring(String s) {
+		if (s == null || s.length() == 0) {
+			return s;
+		}
+		int N = s.length();
+		char[] str = s.toCharArray();
+		int min = Integer.MAX_VALUE;
+		int max = Integer.MIN_VALUE;
+		for (char cha : str) {
+			min = Math.min(min, cha);
+			max = Math.max(max, cha);
+		}
+		int[] arr = new int[N];
+		for (int i = 0; i < N; i++) {
+			arr[i] = str[i] - min + 1;
+		}
+		DC3 dc3 = new DC3(arr, max - min + 1);
+		return s.substring(dc3.sa[N - 1]);
+	}
+
+	public static class DC3 {
+
+		public int[] sa;
+
+		public int[] rank;
+
+		public DC3(int[] nums, int max) {
+			sa = sa(nums, max);
+			rank = rank();
+		}
+
+		private int[] sa(int[] nums, int max) {
+			int n = nums.length;
+			int[] arr = new int[n + 3];
+			for (int i = 0; i < n; i++) {
+				arr[i] = nums[i];
+			}
+			return skew(arr, n, max);
+		}
+
+		private int[] skew(int[] nums, int n, int K) {
+			int n0 = (n + 2) / 3, n1 = (n + 1) / 3, n2 = n / 3, n02 = n0 + n2;
+			int[] s12 = new int[n02 + 3], sa12 = new int[n02 + 3];
+			for (int i = 0, j = 0; i < n + (n0 - n1); ++i) {
+				if (0 != i % 3) {
+					s12[j++] = i;
+				}
+			}
+			radixPass(nums, s12, sa12, 2, n02, K);
+			radixPass(nums, sa12, s12, 1, n02, K);
+			radixPass(nums, s12, sa12, 0, n02, K);
+			int name = 0, c0 = -1, c1 = -1, c2 = -1;
+			for (int i = 0; i < n02; ++i) {
+				if (c0 != nums[sa12[i]] || c1 != nums[sa12[i] + 1] || c2 != nums[sa12[i] + 2]) {
+					name++;
+					c0 = nums[sa12[i]];
+					c1 = nums[sa12[i] + 1];
+					c2 = nums[sa12[i] + 2];
+				}
+				if (1 == sa12[i] % 3) {
+					s12[sa12[i] / 3] = name;
+				} else {
+					s12[sa12[i] / 3 + n0] = name;
+				}
+			}
+			if (name < n02) {
+				sa12 = skew(s12, n02, name);
+				for (int i = 0; i < n02; i++) {
+					s12[sa12[i]] = i + 1;
+				}
+			} else {
+				for (int i = 0; i < n02; i++) {
+					sa12[s12[i] - 1] = i;
+				}
+			}
+			int[] s0 = new int[n0], sa0 = new int[n0];
+			for (int i = 0, j = 0; i < n02; i++) {
+				if (sa12[i] < n0) {
+					s0[j++] = 3 * sa12[i];
+				}
+			}
+			radixPass(nums, s0, sa0, 0, n0, K);
+			int[] sa = new int[n];
+			for (int p = 0, t = n0 - n1, k = 0; k < n; k++) {
+				int i = sa12[t] < n0 ? sa12[t] * 3 + 1 : (sa12[t] - n0) * 3 + 2;
+				int j = sa0[p];
+				if (sa12[t] < n0 ? leq(nums[i], s12[sa12[t] + n0], nums[j], s12[j / 3])
+						: leq(nums[i], nums[i + 1], s12[sa12[t] - n0 + 1], nums[j], nums[j + 1], s12[j / 3 + n0])) {
+					sa[k] = i;
+					t++;
+					if (t == n02) {
+						for (k++; p < n0; p++, k++) {
+							sa[k] = sa0[p];
+						}
+					}
+				} else {
+					sa[k] = j;
+					p++;
+					if (p == n0) {
+						for (k++; t < n02; t++, k++) {
+							sa[k] = sa12[t] < n0 ? sa12[t] * 3 + 1 : (sa12[t] - n0) * 3 + 2;
+						}
+					}
+				}
+			}
+			return sa;
+		}
+
+		private void radixPass(int[] nums, int[] input, int[] output, int offset, int n, int k) {
+			int[] cnt = new int[k + 1];
+			for (int i = 0; i < n; ++i) {
+				cnt[nums[input[i] + offset]]++;
+			}
+			for (int i = 0, sum = 0; i < cnt.length; ++i) {
+				int t = cnt[i];
+				cnt[i] = sum;
+				sum += t;
+			}
+			for (int i = 0; i < n; ++i) {
+				output[cnt[nums[input[i] + offset]]++] = input[i];
+			}
+		}
+
+		private boolean leq(int a1, int a2, int b1, int b2) {
+			return a1 < b1 || (a1 == b1 && a2 <= b2);
+		}
+
+		private boolean leq(int a1, int a2, int a3, int b1, int b2, int b3) {
+			return a1 < b1 || (a1 == b1 && leq(a2, a3, b2, b3));
+		}
+
+		private int[] rank() {
+			int n = sa.length;
+			int[] ans = new int[n];
+			for (int i = 0; i < n; i++) {
+				ans[sa[i]] = i + 1;
+			}
+			return ans;
+		}
+
+	}
+
+}
diff --git a/src/class44/Code03_InsertS2MakeMostAlphabeticalOrder.java b/src/class44/Code03_InsertS2MakeMostAlphabeticalOrder.java
new file mode 100644
index 0000000..f533492
--- /dev/null
+++ b/src/class44/Code03_InsertS2MakeMostAlphabeticalOrder.java
@@ -0,0 +1,249 @@
+package class44;
+
+public class Code03_InsertS2MakeMostAlphabeticalOrder {
+
+	// 暴力方法
+	public static String right(String s1, String s2) {
+		if (s1 == null || s1.length() == 0) {
+			return s2;
+		}
+		if (s2 == null || s2.length() == 0) {
+			return s1;
+		}
+		String p1 = s1 + s2;
+		String p2 = s2 + s1;
+		String ans = p1.compareTo(p2) > 0 ? p1 : p2;
+		for (int end = 1; end < s1.length(); end++) {
+			String cur = s1.substring(0, end) + s2 + s1.substring(end);
+			if (cur.compareTo(ans) > 0) {
+				ans = cur;
+			}
+		}
+		return ans;
+	}
+
+	// 正式方法
+	public static String max(String s1, String s2) {
+		if (s1 == null || s1.length() == 0) {
+			return s2;
+		}
+		if (s2 == null || s2.length() == 0) {
+			return s1;
+		}
+		char[] str1 = s1.toCharArray();
+		char[] str2 = s2.toCharArray();
+		int N = str1.length;
+		int M = str2.length;
+		int min = str1[0];
+		int max = str1[0];
+		for (int i = 1; i < N; i++) {
+			min = Math.min(min, str1[i]);
+			max = Math.max(max, str1[i]);
+		}
+		for (int i = 0; i < M; i++) {
+			min = Math.min(min, str2[i]);
+			max = Math.max(max, str2[i]);
+		}
+		int[] all = new int[N + M + 1];
+		int index = 0;
+		for (int i = 0; i < N; i++) {
+			all[index++] = str1[i] - min + 2;
+		}
+		all[index++] = 1;
+		for (int i = 0; i < M; i++) {
+			all[index++] = str2[i] - min + 2;
+		}
+		DC3 dc3 = new DC3(all, max - min + 2);
+		int[] rank = dc3.rank;
+		int comp = N + 1;
+		for (int i = 0; i < N; i++) {
+			if (rank[i] < rank[comp]) {
+				int best = whereSplit(s1, s2, i);
+				return s1.substring(0, best) + s2 + s1.substring(best);
+			}
+		}
+		return s1 + s2;
+	}
+
+	public static class DC3 {
+
+		public int[] sa;
+		public int[] rank;
+
+		public DC3(int[] nums, int max) {
+			sa = sa(nums, max);
+			rank = rank();
+		}
+
+		private int[] sa(int[] nums, int max) {
+			int n = nums.length;
+			int[] arr = new int[n + 3];
+			for (int i = 0; i < n; i++) {
+				arr[i] = nums[i];
+			}
+			return skew(arr, n, max);
+		}
+
+		private int[] skew(int[] nums, int n, int K) {
+			int n0 = (n + 2) / 3, n1 = (n + 1) / 3, n2 = n / 3, n02 = n0 + n2;
+			int[] s12 = new int[n02 + 3], sa12 = new int[n02 + 3];
+			for (int i = 0, j = 0; i < n + (n0 - n1); ++i) {
+				if (0 != i % 3) {
+					s12[j++] = i;
+				}
+			}
+			radixPass(nums, s12, sa12, 2, n02, K);
+			radixPass(nums, sa12, s12, 1, n02, K);
+			radixPass(nums, s12, sa12, 0, n02, K);
+			int name = 0, c0 = -1, c1 = -1, c2 = -1;
+			for (int i = 0; i < n02; ++i) {
+				if (c0 != nums[sa12[i]] || c1 != nums[sa12[i] + 1] || c2 != nums[sa12[i] + 2]) {
+					name++;
+					c0 = nums[sa12[i]];
+					c1 = nums[sa12[i] + 1];
+					c2 = nums[sa12[i] + 2];
+				}
+				if (1 == sa12[i] % 3) {
+					s12[sa12[i] / 3] = name;
+				} else {
+					s12[sa12[i] / 3 + n0] = name;
+				}
+			}
+			if (name < n02) {
+				sa12 = skew(s12, n02, name);
+				for (int i = 0; i < n02; i++) {
+					s12[sa12[i]] = i + 1;
+				}
+			} else {
+				for (int i = 0; i < n02; i++) {
+					sa12[s12[i] - 1] = i;
+				}
+			}
+			int[] s0 = new int[n0], sa0 = new int[n0];
+			for (int i = 0, j = 0; i < n02; i++) {
+				if (sa12[i] < n0) {
+					s0[j++] = 3 * sa12[i];
+				}
+			}
+			radixPass(nums, s0, sa0, 0, n0, K);
+			int[] sa = new int[n];
+			for (int p = 0, t = n0 - n1, k = 0; k < n; k++) {
+				int i = sa12[t] < n0 ? sa12[t] * 3 + 1 : (sa12[t] - n0) * 3 + 2;
+				int j = sa0[p];
+				if (sa12[t] < n0 ? leq(nums[i], s12[sa12[t] + n0], nums[j], s12[j / 3])
+						: leq(nums[i], nums[i + 1], s12[sa12[t] - n0 + 1], nums[j], nums[j + 1], s12[j / 3 + n0])) {
+					sa[k] = i;
+					t++;
+					if (t == n02) {
+						for (k++; p < n0; p++, k++) {
+							sa[k] = sa0[p];
+						}
+					}
+				} else {
+					sa[k] = j;
+					p++;
+					if (p == n0) {
+						for (k++; t < n02; t++, k++) {
+							sa[k] = sa12[t] < n0 ? sa12[t] * 3 + 1 : (sa12[t] - n0) * 3 + 2;
+						}
+					}
+				}
+			}
+			return sa;
+		}
+
+		private void radixPass(int[] nums, int[] input, int[] output, int offset, int n, int k) {
+			int[] cnt = new int[k + 1];
+			for (int i = 0; i < n; ++i) {
+				cnt[nums[input[i] + offset]]++;
+			}
+			for (int i = 0, sum = 0; i < cnt.length; ++i) {
+				int t = cnt[i];
+				cnt[i] = sum;
+				sum += t;
+			}
+			for (int i = 0; i < n; ++i) {
+				output[cnt[nums[input[i] + offset]]++] = input[i];
+			}
+		}
+
+		private boolean leq(int a1, int a2, int b1, int b2) {
+			return a1 < b1 || (a1 == b1 && a2 <= b2);
+		}
+
+		private boolean leq(int a1, int a2, int a3, int b1, int b2, int b3) {
+			return a1 < b1 || (a1 == b1 && leq(a2, a3, b2, b3));
+		}
+
+		private int[] rank() {
+			int n = sa.length;
+			int[] ans = new int[n];
+			for (int i = 0; i < n; i++) {
+				ans[sa[i]] = i + 1;
+			}
+			return ans;
+		}
+
+	}
+
+	public static int whereSplit(String str1, String str2, int first) {
+		int M = str2.length();
+		String bestPrefix = str2;
+		int bestSplit = first;
+		for (int i = first + 1, j = M - 1; i <= Math.min(str1.length(), first + M); i++, j--) {
+			String curPrefix = str1.substring(first, i) + str2.substring(0, j);
+			if (curPrefix.compareTo(bestPrefix) >= 0) {
+				bestPrefix = curPrefix;
+				bestSplit = i;
+			}
+		}
+		return bestSplit;
+	}
+
+	// for test
+	public static String randomNumberString(int len, int range) {
+		char[] str = new char[len];
+		for (int i = 0; i < len; i++) {
+			str[i] = (char) ((int) (Math.random() * range) + '0');
+		}
+		return String.valueOf(str);
+	}
+
+	// for test
+	public static void main(String[] args) {
+		int range = 10;
+		int len = 50;
+		int testTime = 100000;
+		System.out.println("功能测试开始");
+		for (int i = 0; i < testTime; i++) {
+			int s1Len = (int) (Math.random() * len);
+			int s2Len = (int) (Math.random() * len);
+			String s1 = randomNumberString(s1Len, range);
+			String s2 = randomNumberString(s2Len, range);
+			String ans1 = right(s1, s2);
+			String ans2 = max(s1, s2);
+			if (!ans1.equals(ans2)) {
+				System.out.println("Oops!");
+				System.out.println(s1);
+				System.out.println(s2);
+				System.out.println(ans1);
+				System.out.println(ans2);
+				break;
+			}
+		}
+		System.out.println("功能测试结束");
+		System.out.println("==========");
+		System.out.println("性能测试开始");
+
+		int s1Len = 1000000;
+		int s2Len = 50;
+		String s1 = randomNumberString(s1Len, range);
+		String s2 = randomNumberString(s2Len, range);
+		long start = System.currentTimeMillis();
+		max(s1, s2);
+		long end = System.currentTimeMillis();
+		System.out.println("运行时间 : " + (end - start) + " ms");
+		System.out.println("性能测试结束");
+	}
+
+}
diff --git a/src/class44/DC3.java b/src/class44/DC3.java
new file mode 100644
index 0000000..6a43e3b
--- /dev/null
+++ b/src/class44/DC3.java
@@ -0,0 +1,123 @@
+package class44;
+
+public class DC3 {
+
+	public int[] sa;
+
+	public int[] rank;
+
+	public DC3(int[] nums, int max) {
+		sa = sa(nums, max);
+		rank = rank();
+	}
+
+	private int[] sa(int[] nums, int max) {
+		int n = nums.length;
+		int[] arr = new int[n + 3];
+		for (int i = 0; i < n; i++) {
+			arr[i] = nums[i];
+		}
+		return skew(arr, n, max);
+	}
+
+	private int[] skew(int[] nums, int n, int K) {
+		int n0 = (n + 2) / 3, n1 = (n + 1) / 3, n2 = n / 3, n02 = n0 + n2;
+		int[] s12 = new int[n02 + 3], sa12 = new int[n02 + 3];
+		for (int i = 0, j = 0; i < n + (n0 - n1); ++i) {
+			if (0 != i % 3) {
+				s12[j++] = i;
+			}
+		}
+		radixPass(nums, s12, sa12, 2, n02, K);
+		radixPass(nums, sa12, s12, 1, n02, K);
+		radixPass(nums, s12, sa12, 0, n02, K);
+		int name = 0, c0 = -1, c1 = -1, c2 = -1;
+		for (int i = 0; i < n02; ++i) {
+			if (c0 != nums[sa12[i]] || c1 != nums[sa12[i] + 1] || c2 != nums[sa12[i] + 2]) {
+				name++;
+				c0 = nums[sa12[i]];
+				c1 = nums[sa12[i] + 1];
+				c2 = nums[sa12[i] + 2];
+			}
+			if (1 == sa12[i] % 3) {
+				s12[sa12[i] / 3] = name;
+			} else {
+				s12[sa12[i] / 3 + n0] = name;
+			}
+		}
+		if (name < n02) {
+			sa12 = skew(s12, n02, name);
+			for (int i = 0; i < n02; i++) {
+				s12[sa12[i]] = i + 1;
+			}
+		} else {
+			for (int i = 0; i < n02; i++) {
+				sa12[s12[i] - 1] = i;
+			}
+		}
+		int[] s0 = new int[n0], sa0 = new int[n0];
+		for (int i = 0, j = 0; i < n02; i++) {
+			if (sa12[i] < n0) {
+				s0[j++] = 3 * sa12[i];
+			}
+		}
+		radixPass(nums, s0, sa0, 0, n0, K);
+		int[] sa = new int[n];
+		for (int p = 0, t = n0 - n1, k = 0; k < n; k++) {
+			int i = sa12[t] < n0 ? sa12[t] * 3 + 1 : (sa12[t] - n0) * 3 + 2;
+			int j = sa0[p];
+			if (sa12[t] < n0 ? leq(nums[i], s12[sa12[t] + n0], nums[j], s12[j / 3])
+					: leq(nums[i], nums[i + 1], s12[sa12[t] - n0 + 1], nums[j], nums[j + 1], s12[j / 3 + n0])) {
+				sa[k] = i;
+				t++;
+				if (t == n02) {
+					for (k++; p < n0; p++, k++) {
+						sa[k] = sa0[p];
+					}
+				}
+			} else {
+				sa[k] = j;
+				p++;
+				if (p == n0) {
+					for (k++; t < n02; t++, k++) {
+						sa[k] = sa12[t] < n0 ? sa12[t] * 3 + 1 : (sa12[t] - n0) * 3 + 2;
+					}
+				}
+			}
+		}
+		return sa;
+	}
+
+	private void radixPass(int[] nums, int[] input, int[] output, int offset, int n, int k) {
+		int[] cnt = new int[k + 1];
+		for (int i = 0; i < n; ++i) {
+			cnt[nums[input[i] + offset]]++;
+		}
+		for (int i = 0, sum = 0; i < cnt.length; ++i) {
+			int t = cnt[i];
+			cnt[i] = sum;
+			sum += t;
+		}
+		for (int i = 0; i < n; ++i) {
+			output[cnt[nums[input[i] + offset]]++] = input[i];
+		}
+	}
+
+	private boolean leq(int a1, int a2, int b1, int b2) {
+		return a1 < b1 || (a1 == b1 && a2 <= b2);
+	}
+
+	private boolean leq(int a1, int a2, int a3, int b1, int b2, int b3) {
+		return a1 < b1 || (a1 == b1 && leq(a2, a3, b2, b3));
+	}
+
+	private int[] rank() {
+		int n = sa.length;
+		int[] ans = new int[n];
+		for (int i = 0; i < n; i++) {
+			ans[sa[i]] = i + 1;
+		}
+		return ans;
+	}
+
+}
\ No newline at end of file
diff --git a/src/class44/DC3_Algorithm.pdf b/src/class44/DC3_Algorithm.pdf
new file mode 100644
index 0000000..f053a67
Binary files /dev/null and b/src/class44/DC3_Algorithm.pdf differ
diff --git a/src/class45/Code01_BurstBalloons.java b/src/class45/Code01_BurstBalloons.java
new file mode 100644
index 0000000..004fd4d
--- /dev/null
+++ b/src/class45/Code01_BurstBalloons.java
@@ -0,0 +1,85 @@
+package class45;
+
+public class Code01_BurstBalloons {
+
+	public static int maxCoins1(int[] arr) {
+		if (arr == null || arr.length == 0) {
+			return 0;
+		}
+		if (arr.length == 1) {
+			return arr[0];
+		}
+		int N = arr.length;
+		int[] help = new int[N + 2];
+		help[0] = 1;
+		help[N + 1] = 1;
+		for (int i = 0; i < N; i++) {
+			help[i + 1] = arr[i];
+		}
+		return process(help, 1, N);
+	}
+
+	// 打爆arr[L..R]范围上的所有气球，返回最大的分数
+	// 假设arr[L-1]和arr[R+1]一定没有被打爆
+	public static int process(int[] arr, int L, int R) {
+		if (L == R) {// 如果arr[L..R]范围上只有一个气球，直接打爆即可
+			return arr[L - 1] * arr[L] * arr[R + 1];
+		}
+		// 最后打爆arr[L]的方案，和最后打爆arr[R]的方案，先比较一下
+		int max = Math.max(
+				arr[L - 1] * arr[L] * arr[R + 1] + process(arr, L + 1, R),
+				arr[L - 1] * arr[R] * arr[R + 1] + process(arr, L, R - 1));
+		// 尝试中间位置的气球最后被打爆的每一种方案
+		for (int i = L + 1; i < R; i++) {
+			max = Math.max(max,
+					arr[L - 1] * arr[i] * arr[R + 1] + process(arr, L, i - 1)
+							+ process(arr, i + 1, R));
+		}
+		return max;
+	}
+
+	public static int maxCoins2(int[] arr) {
+		if (arr == null || arr.length == 0) {
+			return 0;
+		}
+		if (arr.length == 1) {
+			return arr[0];
+		}
+		int N = arr.length;
+		int[] help = new int[N + 2];
+		help[0] = 1;
+		help[N + 1] = 1;
+		for (int i = 0; i < N; i++) {
+			help[i + 1] = arr[i];
+		}
+		int[][] dp = new int[N + 2][N + 2];
+		for (int i = 1; i <= N; i++) {
+			dp[i][i] = help[i - 1] * help[i] * help[i + 1];
+			System.out.println(dp[i][i]);
+		}
+		for (int L = N; L >= 1; L--) {
+			for (int R = L + 1; R <= N; R++) {
+				// 求解dp[L][R]，表示help[L..R]上打爆所有气球的最大分数
+				// 最后打爆help[L]的方案
+				int finalL = help[L - 1] * help[L] * help[R + 1] + dp[L + 1][R];
+				// 最后打爆help[R]的方案
+				int finalR = help[L - 1] * help[R] * help[R + 1] + dp[L][R - 1];
+				// 最后打爆help[L]的方案，和最后打爆help[R]的方案，先比较一下
+				dp[L][R] = Math.max(finalL, finalR);
+				// 尝试中间位置的气球最后被打爆的每一种方案
+				for (int i = L + 1; i < R; i++) {
+					dp[L][R] = Math.max(dp[L][R], help[L - 1] * help[i]
+							* help[R + 1] + dp[L][i - 1] + dp[i + 1][R]);
+				}
+			}
+		}
+		return dp[1][N];
+	}
+
+	public static void main(String[] args) {
+		int[] arr = { 4, 2, 3, 5, 1, 6 };
+		System.out.println(maxCoins1(arr));
+		System.out.println(maxCoins2(arr));
+	}
+
+}
diff --git a/src/class45/Code02_RemoveBoxes.java b/src/class45/Code02_RemoveBoxes.java
new file mode 100644
index 0000000..6a9f2f8
--- /dev/null
+++ b/src/class45/Code02_RemoveBoxes.java
@@ -0,0 +1,38 @@
+package class45;
+
+public class Code02_RemoveBoxes {
+
+	public int removeBoxes(int[] boxes) {
+		int N = boxes.length;
+		int[][][] dp = new int[N][N][N];
+		return process(boxes, 0, N - 1, 0, dp);
+	}
+
+	// boxes[L....R]，前面还跟着K个boxes[L]
+	// 前面的包袱和L...R所有的数都消掉，最好得分是什么
+	public static int process(int[] boxes, int L, int R, int K, int[][][] dp) {
+		if (L > R) {
+			return 0;
+		}
+		if (dp[L][R][K] != 0) {
+			return dp[L][R][K];
+		}
+		if (L == R) {
+			dp[L][R][K] = (K + 1) * (K + 1);
+			return dp[L][R][K];
+		}
+		while (L < R && boxes[L] == boxes[L + 1]) {
+			L++;
+			K++;
+		}
+		int ans = (K + 1) * (K + 1) + process(boxes, L + 1, R, 0, dp);
+		for (int m = L + 1; m <= R; m++) {
+			if (boxes[L] == boxes[m]) {
+				ans = Math.max(ans, process(boxes, L + 1, m - 1, 0, dp) + process(boxes, m, R, K + 1, dp));
+			}
+		}
+		dp[L][R][K] = ans;
+		return ans;
+	}
+
+}
diff --git a/src/class45/Code03_StrangePrinter.java b/src/class45/Code03_StrangePrinter.java
new file mode 100644
index 0000000..cfcf7ca
--- /dev/null
+++ b/src/class45/Code03_StrangePrinter.java
@@ -0,0 +1,33 @@
+package class45;
+
+public class Code03_StrangePrinter {
+
+	public static int strangePrinter(String s) {
+		if (s == null || s.length() == 0) {
+			return 0;
+		}
+		char[] str = s.toCharArray();
+		int N = str.length;
+		int[][] dp = new int[N][N];
+		dp[N - 1][N - 1] = 1;
+		for (int i = 0; i < N - 1; i++) {
+			dp[i][i] = 1;
+			dp[i][i + 1] = str[i] == str[i + 1] ? 1 : 2;
+		}
+		for (int L = N - 3; L >= 0; L--) {
+			for (int R = L + 2; R < N; R++) {
+
+				// L....R
+
+				dp[L][R] = R - L + 1;
+
+				// L...k-1 k...R
+				for (int k = L + 1; k <= R; k++) {
+					dp[L][R] = Math.min(dp[L][R], dp[L][k - 1] + dp[k][R] - (str[L] == str[k] ? 1 : 0));
+				}
+			}
+		}
+		return dp[0][N - 1];
+	}
+
+}
diff --git a/src/class46/Code01_RestoreWays.java b/src/class46/Code01_RestoreWays.java
new file mode 100644
index 0000000..a4d913e
--- /dev/null
+++ b/src/class46/Code01_RestoreWays.java
@@ -0,0 +1,237 @@
+package class46;
+
+public class Code01_RestoreWays {
+
+	/*
+	 * 整型数组arr长度为n(3 <= n <= 10^4)，最初每个数字是<=200的正数且满足如下条件： 1. 0位置的要求：arr[0] <=
+	 * arr[1] 2. n-1位置的要求：arr[n-1] <= arr[n-2] 3. 中间i位置的要求：arr[i] <= max(arr[i-1],
+	 * arr[i+1]) 但是在arr有些数字丢失了，比如k位置的数字之前是正数，丢失之后k位置的数字为0。 请你根据上述条件，
+	 * 计算可能有多少种不同的arr可以满足以上条件。 比如 [6,0,9] 只有还原成 [6,9,9]满足全部三个条件，所以返回1种。 [6,9,9] 达标
+	 * 
+	 * [ ...... 0 0]
+	 */
+
+	public static int ways0(int[] arr) {
+		return process0(arr, 0);
+	}
+
+	public static int process0(int[] arr, int index) {
+		if (index == arr.length) {
+			return isValid(arr) ? 1 : 0;
+		} else {
+			if (arr[index] != 0) {
+				return process0(arr, index + 1);
+			} else {
+				int ways = 0;
+				for (int v = 1; v < 201; v++) {
+					arr[index] = v;
+					ways += process0(arr, index + 1);
+				}
+				arr[index] = 0;
+				return ways;
+			}
+		}
+	}
+
+	public static boolean isValid(int[] arr) {
+		if (arr[0] > arr[1]) {
+			return false;
+		}
+		if (arr[arr.length - 1] > arr[arr.length - 2]) {
+			return false;
+		}
+		for (int i = 1; i < arr.length - 1; i++) {
+			if (arr[i] > Math.max(arr[i - 1], arr[i + 1])) {
+				return false;
+			}
+		}
+		return true;
+	}
+
+	public static int ways1(int[] arr) {
+		int N = arr.length;
+		if (arr[N - 1] != 0) {
+			return process1(arr, N - 1, arr[N - 1], 2);
+		} else {
+			int ways = 0;
+			for (int v = 1; v < 201; v++) {
+				ways += process1(arr, N - 1, v, 2);
+			}
+			return ways;
+		}
+	}
+
+	// 如果i位置的数字变成了v,
+	// 并且arr[i]和arr[i+1]的关系为s，
+	// s==0，代表arr[i] < arr[i+1] 右大
+	// s==1，代表arr[i] == arr[i+1]
+	// s==2，代表arr[i] > arr[i+1] 右小
+	// 返回0...i范围上有多少种有效的转化方式？
+	public static int process1(int[] arr, int i, int v, int s) {
+		if (i == 0) { // 0...i 只剩一个数了，0...0
+			return ((s == 0 || s == 1) && (arr[i] == 0 || v == arr[i])) ? 1 : 0;
+		}
+		// i > 0
+		if (arr[i] != 0 && v != arr[i]) {
+			return 0;
+		}
+		// i>0 并且 i位置的数真的可以变成V，
+		int ways = 0;
+		if (s == 0 || s == 1) { // [i - 1] [i] <= 右
+			for (int pre = 1; pre < 201; pre++) {
+				ways += process1(arr, i - 1, pre, pre < v ? 0 : (pre == v ? 1 : 2));
+			}
+		} else { // s == 2 i > 右 i-1 >= i > 右
+			for (int pre = v; pre < 201; pre++) {
+				ways += process1(arr, i - 1, pre, pre == v ? 1 : 2);
+			}
+		}
+		return ways;
+	}
+
+	public static int ways2(int[] arr) {
+		int N = arr.length;
+		int[][][] dp = new int[N][201][3];
+		// dp[0][...][...]
+		// dp[0][...][2] = 0
+		// dp[0][...][0] = 1
+		// dp[0][...][1] = 1
+		if (arr[0] != 0) {
+			dp[0][arr[0]][0] = 1;
+			dp[0][arr[0]][1] = 1;
+		} else {
+			for (int v = 1; v < 201; v++) {
+				dp[0][v][0] = 1;
+				dp[0][v][1] = 1;
+			}
+		}
+		for (int i = 1; i < N; i++) {
+			for (int v = 1; v < 201; v++) {
+				for (int s = 0; s < 3; s++) {
+					if (arr[i] == 0 || v == arr[i]) {
+						if (s == 0 || s == 1) {
+							for (int pre = 1; pre < 201; pre++) {
+								dp[i][v][s] += dp[i - 1][pre][pre < v ? 0 : (pre == v ? 1 : 2)];
+							}
+						} else {
+							for (int pre = v; pre < 201; pre++) {
+								dp[i][v][s] += dp[i - 1][pre][pre < v ? 0 : (pre == v ? 1 : 2)];
+							}
+						}
+					}
+				}
+			}
+		}
+		if (arr[N - 1] != 0) {
+			return dp[N - 1][arr[N - 1]][2];
+		} else {
+			int ways = 0;
+			for (int v = 1; v < 201; v++) {
+				ways += dp[N - 1][v][2];
+			}
+			return ways;
+		}
+	}
+
+	public static int ways3(int[] arr) {
+		int N = arr.length;
+		int[][][] dp = new int[N][201][3];
+		if (arr[0] != 0) {
+			dp[0][arr[0]][0] = 1;
+			dp[0][arr[0]][1] = 1;
+		} else {
+			for (int v = 1; v < 201; v++) {
+				dp[0][v][0] = 1;
+				dp[0][v][1] = 1;
+			}
+		}
+		// presum[0~V][0] -> sum0[]
+		// presum[0~V][1] -> sum1[]
+		// presum[0~V][2] -> sum2[]
+		int[][] presum = new int[201][3];
+		// presum -> dp[0][..][..] 三张表
+		for (int v = 1; v < 201; v++) {
+			for (int s = 0; s < 3; s++) {
+				presum[v][s] = presum[v - 1][s] + dp[0][v][s];
+			}
+		}
+		for (int i = 1; i < N; i++) {
+			for (int v = 1; v < 201; v++) {
+				for (int s = 0; s < 3; s++) {
+					if (arr[i] == 0 || v == arr[i]) {
+						if (s == 0 || s == 1) {
+							// dp[i][..][..] -> dp[i-1][..][..]
+							dp[i][v][s] += sum(1, v - 1, 0, presum);
+							dp[i][v][s] += dp[i - 1][v][1];
+							dp[i][v][s] += sum(v + 1, 200, 2, presum);
+						} else {
+							dp[i][v][s] += dp[i - 1][v][1];
+							dp[i][v][s] += sum(v + 1, 200, 2, presum);
+						}
+					}
+				}
+			}
+			for (int v = 1; v < 201; v++) {
+				for (int s = 0; s < 3; s++) {
+					presum[v][s] = presum[v - 1][s] + dp[i][v][s];
+				}
+			}
+		}
+		if (arr[N - 1] != 0) {
+			return dp[N - 1][arr[N - 1]][2];
+		} else {
+			return sum(1, 200, 2, presum);
+		}
+	}
+
+	public static int sum(int begin, int end, int relation, int[][] presum) {
+		return presum[end][relation] - presum[begin - 1][relation];
+	}
+
+	// for test
+	public static int[] generateRandomArray(int len) {
+		int[] ans = new int[(int) (Math.random() * len) + 2];
+		for (int i = 0; i < ans.length; i++) {
+			if (Math.random() < 0.5) {
+				ans[i] = 0;
+			} else {
+				ans[i] = (int) (Math.random() * 200) + 1;
+			}
+		}
+		return ans;
+	}
+
+	// for test
+	public static void printArray(int[] arr) {
+		System.out.println("arr size : " + arr.length);
+		for (int i = 0; i < arr.length; i++) {
+			System.out.print(arr[i] + " ");
+		}
+		System.out.println();
+	}
+
+	public static void main(String[] args) {
+		int len = 3;
+		int testTime = 10;
+		System.out.println("test begin");
+		for (int i = 0; i < testTime; i++) {
+			int[] arr = generateRandomArray(len);
+			int ans0 = ways0(arr);
+			int ans1 = ways1(arr);
+			int ans2 = ways2(arr);
+			int ans3 = ways3(arr);
+			if (ans0 != ans1 || ans2 != ans3 || ans0 != ans2) {
+				System.out.println("Oops!");
+			}
+		}
+		System.out.println("test finish");
+		int[] arr = generateRandomArray(100000);
+		System.out.println(arr.length);
+		long begin = System.currentTimeMillis();
+		ways3(arr);
+		long end = System.currentTimeMillis();
+		System.out.println("run time : " + (end - begin) + " ms");
+
+	}
+
+}
diff --git a/src/class46/Code02_DeleteAdjacentSameCharacter.java b/src/class46/Code02_DeleteAdjacentSameCharacter.java
new file mode 100644
index 0000000..bc94ccb
--- /dev/null
+++ b/src/class46/Code02_DeleteAdjacentSameCharacter.java
@@ -0,0 +1,172 @@
+package class46;
+
+// 如果一个字符相邻的位置没有相同字符，那么这个位置的字符出现不能被消掉
+// 比如:"ab"，其中a和b都不能被消掉
+// 如果一个字符相邻的位置有相同字符，就可以一起消掉
+// 比如:"abbbc"，中间一串的b是可以被消掉的，消除之后剩下"ac"
+// 某些字符如果消掉了，剩下的字符认为重新靠在一起
+// 给定一个字符串，你可以决定每一步消除的顺序，目标是请尽可能多的消掉字符，返回最少的剩余字符数量
+// 比如："aacca", 如果先消掉最左侧的"aa"，那么将剩下"cca"，然后把"cc"消掉，剩下的"a"将无法再消除，返回1
+// 但是如果先消掉中间的"cc"，那么将剩下"aaa"，最后都消掉就一个字符也不剩了，返回0，这才是最优解。
+// 再比如："baaccabb"，
+// 如果先消除最左侧的两个a，剩下"bccabb"，
+// 如果再消除最左侧的两个c，剩下"babb"，
+// 最后消除最右侧的两个b，剩下"ba"无法再消除，返回2
+// 而最优策略是：
+// 如果先消除中间的两个c，剩下"baaabb"，
+// 如果再消除中间的三个a，剩下"bbb"，
+// 最后消除三个b，不留下任何字符，返回0，这才是最优解
+public class Code02_DeleteAdjacentSameCharacter {
+
+	// 暴力解
+	public static int restMin1(String s) {
+		if (s == null) {
+			return 0;
+		}
+		if (s.length() < 2) {
+			return s.length();
+		}
+		int minLen = s.length();
+		for (int L = 0; L < s.length(); L++) {
+			for (int R = L + 1; R < s.length(); R++) {
+				if (canDelete(s.substring(L, R + 1))) {
+					minLen = Math.min(minLen, restMin1(s.substring(0, L) + s.substring(R + 1, s.length())));
+				}
+			}
+		}
+		return minLen;
+	}
+
+	public static boolean canDelete(String s) {
+		char[] str = s.toCharArray();
+		for (int i = 1; i < str.length; i++) {
+			if (str[i - 1] != str[i]) {
+				return false;
+			}
+		}
+		return true;
+	}
+
+	// 优良尝试的暴力递归版本
+	public static int restMin2(String s) {
+		if (s == null) {
+			return 0;
+		}
+		if (s.length() < 2) {
+			return s.length();
+		}
+		char[] str = s.toCharArray();
+		return process(str, 0, str.length - 1, false);
+	}
+
+	public static int process(char[] str, int L, int R, boolean has) {
+		if (L > R) {
+			return 0;
+		}
+		if (L == R) {
+			return has ? 0 : 1;
+		}
+		int index = L;
+		int K = has ? 1 : 0;
+		while (index <= R && str[index] == str[L]) {
+			K++;
+			index++;
+		}
+		int way1 = (K > 1 ? 0 : 1) + process(str, index, R, false);
+		int way2 = Integer.MAX_VALUE;
+		for (int split = index; split <= R; split++) {
+			if (str[split] == str[L] && str[split] != str[split - 1]) {
+				if (process(str, index, split - 1, false) == 0) {
+					way2 = Math.min(way2, process(str, split, R, K != 0));
+				}
+			}
+		}
+		return Math.min(way1, way2);
+	}
+
+	// 优良尝试的动态规划版本
+	public static int restMin3(String s) {
+		if (s == null) {
+			return 0;
+		}
+		if (s.length() < 2) {
+			return s.length();
+		}
+		char[] str = s.toCharArray();
+		int N = str.length;
+		int[][][] dp = new int[N][N][2];
+		for (int i = 0; i < N; i++) {
+			for (int j = 0; j < N; j++) {
+				for (int k = 0; k < 2; k++) {
+					dp[i][j][k] = -1;
+				}
+			}
+		}
+		return dpProcess(str, 0, N - 1, false, dp);
+	}
+
+	public static int dpProcess(char[] str, int L, int R, boolean has, int[][][] dp) {
+		if (L > R) {
+			return 0;
+		}
+		int K = has ? 1 : 0;
+		if (dp[L][R][K] != -1) {
+			return dp[L][R][K];
+		}
+		int ans = 0;
+		if (L == R) {
+			ans = (K == 0 ? 1 : 0);
+		} else {
+			int index = L;
+			int all = K;
+			while (index <= R && str[index] == str[L]) {
+				all++;
+				index++;
+			}
+			int way1 = (all > 1 ? 0 : 1) + dpProcess(str, index, R, false, dp);
+			int way2 = Integer.MAX_VALUE;
+			for (int split = index; split <= R; split++) {
+				if (str[split] == str[L] && str[split] != str[split - 1]) {
+					if (dpProcess(str, index, split - 1, false, dp) == 0) {
+						way2 = Math.min(way2, dpProcess(str, split, R, all > 0, dp));
+					}
+				}
+			}
+			ans = Math.min(way1, way2);
+		}
+		dp[L][R][K] = ans;
+		return ans;
+	}
+
+	public static String randomString(int len, int variety) {
+		char[] str = new char[len];
+		for (int i = 0; i < len; i++) {
+			str[i] = (char) ((int) (Math.random() * variety) + 'a');
+		}
+		return String.valueOf(str);
+	}
+
+	public static void main(String[] args) {
+		int maxLen = 16;
+		int variety = 3;
+		int testTime = 100000;
+		System.out.println("测试开始");
+		for (int i = 0; i < testTime; i++) {
+			int len = (int) (Math.random() * maxLen);
+			String str = randomString(len, variety);
+			int ans1 = restMin1(str);
+			int ans2 = restMin2(str);
+			int ans3 = restMin3(str);
+			if (ans1 != ans2 || ans1 != ans3) {
+				System.out.println(str);
+				System.out.println(ans1);
+				System.out.println(ans2);
+				System.out.println(ans3);
+				System.out.println("出错了！");
+				break;
+			}
+		}
+		System.out.println("测试结束");
+	}
+
+}