modify code on class

src/class08_13/Code01_IsCBT.java

@@ -30,9 +30,7 @@ public class Code01_IsCBT {
 			r = head.right;
 			if (
 			// 如果遇到了不双全的节点之后，又发现当前节点不是叶节点
-			    (leaf && (l != null || r != null)) 
-			    || 
-			    (l == null && r != null)
+			(leaf && (l != null || r != null)) || (l == null && r != null)
 
 			) {
 				return false;
@@ -51,13 +49,9 @@ public class Code01_IsCBT {
 	}
 
 	public static boolean isCBT2(Node head) {
-		if (head == null) {
-			return true;
-		}
 		return process(head).isCBT;
 	}
 
-	// 对每一棵子树，是否是满二叉树、是否是完全二叉树、高度
 	public static class Info {
 		public boolean isFull;
 		public boolean isCBT;
@@ -70,49 +64,23 @@ public class Code01_IsCBT {
 		}
 	}
 
-	public static Info process(Node X) {
-		if (X == null) {
+	public static Info process(Node x) {
+		if (x == null) {
 			return new Info(true, true, 0);
 		}
-		Info leftInfo = process(X.left);
-		Info rightInfo = process(X.right);
-		
-		
-		
+		Info leftInfo = process(x.left);
+		Info rightInfo = process(x.right);
 		int height = Math.max(leftInfo.height, rightInfo.height) + 1;
-		
-		
-		boolean isFull = leftInfo.isFull 
-				&& 
-				rightInfo.isFull 
-				&& leftInfo.height == rightInfo.height;
-		
-		
+		boolean isFull = leftInfo.isFull && rightInfo.isFull && leftInfo.height == rightInfo.height;
 		boolean isCBT = false;
-		if (isFull) {
+		if (leftInfo.isFull && rightInfo.isFull && leftInfo.height == rightInfo.height) {
+			isCBT = true;
+		} else if (leftInfo.isCBT && rightInfo.isFull && leftInfo.height == rightInfo.height + 1) {
+			isCBT = true;
+		} else if (leftInfo.isFull && rightInfo.isFull && leftInfo.height == rightInfo.height + 1) {
+			isCBT = true;
+		} else if (leftInfo.isFull && rightInfo.isCBT && leftInfo.height == rightInfo.height) {
 			isCBT = true;
-		} else { // 以x为头整棵树，不满
-			if (leftInfo.isCBT && rightInfo.isCBT) {
-				
-				
-				if (leftInfo.isCBT 
-						&& rightInfo.isFull 
-						&& leftInfo.height == rightInfo.height + 1) {
-					isCBT = true;
-				}
-				if (leftInfo.isFull 
-						&& 
-						rightInfo.isFull 
-						&& leftInfo.height == rightInfo.height + 1) {
-					isCBT = true;
-				}
-				if (leftInfo.isFull 
-						&& rightInfo.isCBT && leftInfo.height == rightInfo.height) {
-					isCBT = true;
-				}
-				
-				
-			}
 		}
 		return new Info(isFull, isCBT, height);
 	}

src/class08_13/Code03_lowestAncestor.java

@@ -49,49 +49,41 @@ public class Code03_lowestAncestor {
 		}
 	}
 
-	public static Node lowestAncestor2(Node head, Node o1, Node o2) {
-		return process(head, o1, o2).ans;
+	public static Node lowestAncestor2(Node head, Node a, Node b) {
+		return process(head, a, b).ans;
 	}
 
-	// 任何子树，
 	public static class Info {
+		public boolean findA;
+		public boolean findB;
 		public Node ans;
-		public boolean findO1;
-		public boolean findO2;
 
-		public Info(Node a, boolean f1, boolean f2) {
-			ans = a;
-			findO1 = f1;
-			findO2 = f2;
+		public Info(boolean fA, boolean fB, Node an) {
+			findA = fA;
+			findB = fB;
+			ans = an;
 		}
 	}
 
-	public static Info process(Node X, Node o1, Node o2) {
-		if (X == null) {
-			return new Info(null, false, false);
+	public static Info process(Node x, Node a, Node b) {
+		if (x == null) {
+			return new Info(false, false, null);
 		}
-		Info leftInfo = process(X.left, o1, o2);
-		Info rightInfo = process(X.right, o1, o2);
-		boolean findO1 = X == o1 || leftInfo.findO1 || rightInfo.findO1;
-		boolean findO2 = X == o2 || leftInfo.findO2 || rightInfo.findO2;
-		// 	O1和O2最初的交汇点在哪？
-		// 1) 在左树上已经提前交汇了
-		// 2) 在右树上已经提前交汇了
-		// 3) 没有在左树或者右树上提前交汇，O1  O2 全了
-		// 4) 
+		Info leftInfo = process(x.left, a, b);
+		Info rightInfo = process(x.right, a, b);
+		boolean findA = (x == a) || leftInfo.findA || rightInfo.findA;
+		boolean findB = (x == b) || leftInfo.findB || rightInfo.findB;
 		Node ans = null;
 		if (leftInfo.ans != null) {
 			ans = leftInfo.ans;
-		}
-		if (rightInfo.ans != null) {
+		} else if (rightInfo.ans != null) {
 			ans = rightInfo.ans;
-		}
-		if (ans == null) {
-			if (findO1 && findO2) {
-				ans = X;
+		} else {
+			if (findA && findB) {
+				ans = x;
 			}
 		}
-		return new Info(ans, findO1, findO2);
+		return new Info(findA, findB, ans);
 	}
 
 	// for test

src/class08_13/Code04_MaxHappy.java

@@ -46,36 +46,34 @@ public class Code04_MaxHappy {
 		}
 	}
 
-	public static int maxHappy2(Employee boss) {
-		if (boss == null) {
-			return 0;
-		}
-		Info all = process2(boss);
-		return Math.max(all.yes, all.no);
+	public static int maxHappy2(Employee head) {
+		Info allInfo = process(head);
+		return Math.max(allInfo.no, allInfo.yes);
 	}
 
 	public static class Info {
-		public int yes;
 		public int no;
+		public int yes;
 
-		public Info(int y, int n) {
-			yes = y;
+		public Info(int n, int y) {
 			no = n;
+			yes = y;
 		}
 	}
 
-	public static Info process2(Employee x) {
-		if (x.nexts.isEmpty()) {
-			return new Info(x.happy, 0);
+	public static Info process(Employee x) {
+		if (x == null) {
+			return new Info(0, 0);
 		}
-		int yes = x.happy;
 		int no = 0;
+		int yes = x.happy;
 		for (Employee next : x.nexts) {
-			Info nextInfo = process2(next);
+			Info nextInfo = process(next);
+			no += Math.max(nextInfo.no, nextInfo.yes);
 			yes += nextInfo.no;
-			no += Math.max(nextInfo.yes, nextInfo.no);
+
 		}
-		return new Info(yes, no);
+		return new Info(no, yes);
 	}
 
 	// for test

src/class09_13/Code01_LowestLexicography.java

@@ -1,9 +1,8 @@
 package class09_13;
 
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Comparator;
-import java.util.HashSet;
+import java.util.TreeSet;
 
 public class Code01_LowestLexicography {
 
@@ -11,34 +10,41 @@ public class Code01_LowestLexicography {
 		if (strs == null || strs.length == 0) {
 			return "";
 		}
-		ArrayList<String> all = new ArrayList<>();
-		HashSet<Integer> use = new HashSet<>();
-		process(strs, use, "", all);
-		String lowest = all.get(0);
-		for (int i = 1; i < all.size(); i++) {
-			if (all.get(i).compareTo(lowest) < 0) {
-				lowest = all.get(i);
+		TreeSet<String> ans = process(strs);
+		return ans.size() == 0 ? "" : ans.first();
+	}
+
+	// strs中所有字符串全排列，返回所有可能的结果
+	public static TreeSet<String> process(String[] strs) {
+		TreeSet<String> ans = new TreeSet<>();
+		if (strs.length == 0) {
+			ans.add("");
+			return ans;
+		}
+		for (int i = 0; i < strs.length; i++) {
+			String first = strs[i];
+			String[] nexts = removeIndexString(strs, i);
+			TreeSet<String> next = process(nexts);
+			for (String cur : next) {
+				ans.add(first + cur);
 			}
 		}
-		return lowest;
+		return ans;
 	}
 
-	// strs里放着所有的字符串
-	// 已经使用过的字符串的下标，在use里登记了，不要再使用了
-	// 之前使用过的字符串，拼接成了-> path
-	// 用all收集所有可能的拼接结果
-	public static void process(String[] strs, HashSet<Integer> use, String path, ArrayList<String> all) {
-		if (use.size() == strs.length) {
-			all.add(path);
-		} else {
-			for (int i = 0; i < strs.length; i++) {
-				if (!use.contains(i)) {
-					use.add(i);
-					process(strs, use, path + strs[i], all);
-					use.remove(i);
-				}
+	// {"abc", "cks", "bct"}
+	// 0 1 2
+	// removeIndexString(arr , 1) -> {"abc", "bct"}
+	public static String[] removeIndexString(String[] arr, int index) {
+		int N = arr.length;
+		String[] ans = new String[N - 1];
+		int ansIndex = 0;
+		for (int i = 0; i < N; i++) {
+			if (i != index) {
+				ans[ansIndex++] = arr[i];
 			}
 		}
+		return ans;
 	}
 
 	public static class MyComparator implements Comparator<String> {
@@ -91,13 +97,7 @@ public class Code01_LowestLexicography {
 	public static void main(String[] args) {
 		int arrLen = 6;
 		int strLen = 5;
-		int testTimes = 100000;
-		String[] arr = generateRandomStringArray(arrLen, strLen);
-		System.out.println("先打印一个生成的字符串");
-		for (String str : arr) {
-			System.out.print(str + ",");
-		}
-		System.out.println();
+		int testTimes = 10000;
 		System.out.println("test begin");
 		for (int i = 0; i < testTimes; i++) {
 			String[] arr1 = generateRandomStringArray(arrLen, strLen);