Merge branch 'master' of https://github.com/algorithmzuo/algorithmbasic2020 into zuo-master

src/class01/Code01_SelectionSort.java

@@ -1,4 +1,4 @@
-package class01_01;
+package class01;
 
 import java.util.Arrays;
 

src/class01/Code02_BubbleSort.java

@@ -1,4 +1,4 @@
-package class01_01;
+package class01;
 
 import java.util.Arrays;
 

src/class01/Code03_InsertionSort.java

@@ -1,4 +1,4 @@
-package class01_01;
+package class01;
 
 import java.util.Arrays;
 

src/class01/Code04_BSExist.java

@@ -1,4 +1,4 @@
-package class01_01;
+package class01;
 
 import java.util.Arrays;
 

src/class01/Code05_BSNearLeft.java

@@ -1,4 +1,4 @@
-package class01_01;
+package class01;
 
 import java.util.Arrays;
 

src/class01/Code05_BSNearRight.java

@@ -1,4 +1,4 @@
-package class01_01;
+package class01;
 
 import java.util.Arrays;
 

src/class01/Code06_BSAwesome.java

@@ -1,4 +1,4 @@
-package class01_01;
+package class01;
 
 public class Code06_BSAwesome {
 

src/class02/Code01_Swap.java

@@ -1,4 +1,4 @@
-package class01_02;
+package class02;
 
 public class Code01_Swap {
 	

src/class02/Code02_EvenTimesOddTimes.java

@@ -1,4 +1,4 @@
-package class01_02;
+package class02;
 
 public class Code02_EvenTimesOddTimes {
 

src/class02/Code03_KM.java

@@ -1,4 +1,4 @@
-package class01_02;
+package class02;
 
 import java.util.HashMap;
 import java.util.HashSet;

src/class03/Code01_ReverseList.java

@@ -1,4 +1,4 @@
-package class02_03;
+package class03;
 
 import java.util.ArrayList;
 import java.util.List;

src/class03/Code02_DeleteGivenValue.java

@@ -1,4 +1,4 @@
-package class02_03;
+package class03;
 
 public class Code02_DeleteGivenValue {
 

src/class03/Code03_DoubleEndsQueueToStackAndQueue.java

@@ -1,4 +1,4 @@
-package class02_03;
+package class03;
 
 import java.util.LinkedList;
 import java.util.Queue;

src/class03/Code04_RingArray.java

@@ -1,4 +1,4 @@
-package class02_03;
+package class03;
 
 public class Code04_RingArray {
 

src/class03/Code05_GetMinStack.java

@@ -1,4 +1,4 @@
-package class02_03;
+package class03;
 
 import java.util.Stack;
 

src/class03/Code06_TwoStacksImplementQueue.java

@@ -1,4 +1,4 @@
-package class02_03;
+package class03;
 
 import java.util.Stack;
 

src/class03/Code07_TwoQueueImplementStack.java

@@ -1,4 +1,4 @@
-package class02_03;
+package class03;
 
 import java.util.LinkedList;
 import java.util.Queue;

src/class03/Code08_GetMax.java

@@ -1,4 +1,4 @@
-package class02_03;
+package class03;
 
 public class Code08_GetMax {
 

src/class03/HashMapAndSortedMap.java

@@ -1,4 +1,4 @@
-package class02_03;
+package class03;
 
 import java.util.HashMap;
 import java.util.HashSet;

src/class04/Code01_MergeSort.java

@@ -1,4 +1,4 @@
-package class03_04;
+package class04;
 
 public class Code01_MergeSort {
 

src/class04/Code02_SmallSum.java

@@ -1,4 +1,4 @@
-package class03_04;
+package class04;
 
 public class Code02_SmallSum {
 

src/class04/Code03_ReversePair.java

@@ -1,4 +1,4 @@
-package class03_04;
+package class04;
 
 public class Code03_ReversePair {
 

src/class04/Code04_BiggerThanRightTwice.java

@@ -1,4 +1,4 @@
-package class03_04;
+package class04;
 
 public class Code04_BiggerThanRightTwice {
 

src/class05/Code01_CountOfRangeSum.java

@@ -1,4 +1,4 @@
-package class03_05;
+package class05;
 
 // 这道题直接在leetcode测评：
 // https://leetcode.com/problems/count-of-range-sum/

src/class05/Code02_PartitionAndQuickSort.java

@@ -1,4 +1,4 @@
-package class03_05;
+package class05;
 
 public class Code02_PartitionAndQuickSort {
 

src/class05/Code03_QuickSortRecursiveAndUnrecursive.java

@@ -1,4 +1,4 @@
-package class03_05;
+package class05;
 
 import java.util.Stack;
 

src/class06/Code01_Comparator.java

@@ -1,4 +1,4 @@
-package class04_06;
+package class06;
 
 import java.util.ArrayList;
 import java.util.Arrays;

src/class06/Code02_Heap.java

@@ -1,4 +1,4 @@
-package class04_06;
+package class06;
 
 import java.util.Comparator;
 import java.util.PriorityQueue;

src/class06/Code03_HeapSort.java

@@ -1,4 +1,4 @@
-package class04_06;
+package class06;
 
 import java.util.Arrays;
 import java.util.PriorityQueue;

src/class06/Code04_SortArrayDistanceLessK.java

@@ -1,4 +1,4 @@
-package class04_06;
+package class06;
 
 import java.util.Arrays;
 import java.util.PriorityQueue;

src/class07/Code01_CoverMax.java

@@ -1,4 +1,4 @@
-package class04_07;
+package class07;
 
 import java.util.Arrays;
 import java.util.Comparator;

src/class07/Code02_EveryStepShowBoss.java

@@ -1,4 +1,4 @@
-package class04_07;
+package class07;
 
 import java.util.ArrayList;
 import java.util.Comparator;

src/class07/HeapGreater.java

@@ -1,4 +1,4 @@
-package class04_07;
+package class07;
 
 import java.util.ArrayList;
 import java.util.Comparator;

src/class07/Inner.java

@@ -1,4 +1,4 @@
-package class04_07;
+package class07;
 
 public class Inner<T> {
 	public T value;

src/class08/Code01_TrieTree.java

@@ -1,4 +1,4 @@
-package class05_08;
+package class08;
 
 import java.util.HashMap;
 

src/class08/Code02_TrieTree.java

@@ -1,4 +1,4 @@
-package class05_08;
+package class08;
 
 import java.util.HashMap;
 

src/class08/Code03_CountSort.java

@@ -1,4 +1,4 @@
-package class05_08;
+package class08;
 
 import java.util.Arrays;
 

src/class08/Code04_RadixSort.java

@@ -1,4 +1,4 @@
-package class05_08;
+package class08;
 
 import java.util.Arrays;
 

src/class09/Code01_LinkedListMid.java

@@ -1,4 +1,4 @@
-package class06_09;
+package class09;
 
 import java.util.ArrayList;
 

src/class09/Code02_IsPalindromeList.java

@@ -1,4 +1,4 @@
-package class06_09;
+package class09;
 
 import java.util.Stack;
 

src/class09/Code03_SmallerEqualBigger.java

@@ -1,4 +1,4 @@
-package class06_09;
+package class09;
 
 public class Code03_SmallerEqualBigger {
 

src/class09/Code04_CopyListWithRandom.java

@@ -1,4 +1,4 @@
-package class06_09;
+package class09;
 
 import java.util.HashMap;
 

src/class10/Code01_FindFirstIntersectNode.java

@@ -1,4 +1,4 @@
-package class06_10;
+package class10;
 
 public class Code01_FindFirstIntersectNode {
 

src/class10/Code02_RecursiveTraversalBT.java

@@ -1,6 +1,6 @@
-package class07_10;
+package class10;
 
-public class Code01_RecursiveTraversalBT {
+public class Code02_RecursiveTraversalBT {
 
 	public static class Node {
 		public int value;

src/class10/Code03_UnRecursiveTraversalBT.java

@@ -1,8 +1,8 @@
-package class07_10;
+package class10;
 
 import java.util.Stack;
 
-public class Code02_UnRecursiveTraversalBT {
+public class Code03_UnRecursiveTraversalBT {
 
 	public static class Node {
 		public int value;

src/class11/Code01_LevelTraversalBT.java

@@ -1,4 +1,4 @@
-package class07_11;
+package class11;
 
 import java.util.LinkedList;
 import java.util.Queue;

src/class11/Code02_SerializeAndReconstructTree.java

@@ -1,4 +1,4 @@
-package class07_11;
+package class11;
 
 import java.util.LinkedList;
 import java.util.Queue;

src/class11/Code03_EncodeNaryTreeToBinaryTree.java

@@ -1,4 +1,4 @@
-package class07_11;
+package class11;
 
 import java.util.ArrayList;
 import java.util.List;

src/class11/Code04_PrintBinaryTree.java

@@ -1,4 +1,4 @@
-package class07_11;
+package class11;
 
 public class Code04_PrintBinaryTree {
 

src/class11/Code05_TreeMaxWidth.java

@@ -1,4 +1,4 @@
-package class07_11;
+package class11;
 
 import java.util.HashMap;
 import java.util.LinkedList;

src/class11/Code06_SuccessorNode.java

@@ -1,4 +1,4 @@
-package class07_11;
+package class11;
 
 public class Code06_SuccessorNode {
 

src/class11/Code07_PaperFolding.java

@@ -1,4 +1,4 @@
-package class07_11;
+package class11;
 
 public class Code07_PaperFolding {
 

src/class11_17/Code03_PrintAllPermutations.java

@@ -1,88 +0,0 @@
-package class11_17;
-
-import java.util.ArrayList;
-import java.util.List;
-
-public class Code03_PrintAllPermutations {
-
-	public static ArrayList<String> permutation(String str) {
-		ArrayList<String> res = new ArrayList<>();
-		if (str == null || str.length() == 0) {
-			return res;
-		}
-		char[] chs = str.toCharArray();
-		process(chs, 0, res);
-		return res;
-	}
-
-	// str[0..i-1]已经做好决定的
-	// str[i...]都有机会来到i位置
-	// i终止位置，str当前的样子，就是一种结果 -> ans
-	public static void process(char[] str, int i, ArrayList<String> ans) {
-		if (i == str.length) {
-			ans.add(String.valueOf(str));
-		}
-		// 如果i没有终止，i...  都可以来到i位置
-		for (int j = i; j < str.length; j++) { // j  i后面所有的字符都有机会
-			swap(str, i, j);
-			process(str, i + 1, ans);
-			swap(str, i, j);
-		}
-	}
-	
-
-	public static ArrayList<String> permutationNoRepeat(String str) {
-		ArrayList<String> res = new ArrayList<>();
-		if (str == null || str.length() == 0) {
-			return res;
-		}
-		char[] chs = str.toCharArray();
-		process2(chs, 0, res);
-		return res;
-	}
-
-	// str[0..i-1]已经做好决定的
-	// str[i...]都有机会来到i位置
-	// i终止位置，str当前的样子，就是一种结果 -> ans
-	public static void process2(char[] str, int i, ArrayList<String> res) {
-		if (i == str.length) {
-			res.add(String.valueOf(str));
-			return;
-		}
-		boolean[] visit = new boolean[26]; // visit[0 1 .. 25]
-		for (int j = i; j < str.length; j++) {
-			// str[j] = 'a'   -> 0   visit[0] -> 'a'
-			
-			// str[j] = 'z'   -> 25   visit[25] -> 'z'
-			if (!visit[str[j] - 'a']) {
-				
-				visit[str[j] - 'a'] = true;
-				swap(str, i, j);
-				process2(str, i + 1, res);
-				swap(str, i, j);
-				
-			}
-		}
-	}
-
-	public static void swap(char[] chs, int i, int j) {
-		char tmp = chs[i];
-		chs[i] = chs[j];
-		chs[j] = tmp;
-	}
-
-	public static void main(String[] args) {
-		String s = "aac";
-		List<String> ans1 = permutation(s);
-		for (String str : ans1) {
-			System.out.println(str);
-		}
-		System.out.println("=======");
-		List<String> ans2 = permutationNoRepeat(s);
-		for (String str : ans2) {
-			System.out.println(str);
-		}
-
-	}
-
-}

src/class11_17/Code07_Knapsack.java

@@ -1,79 +0,0 @@
-package class11_17;
-
-public class Code07_Knapsack {
-
-	public static int getMaxValue(int[] w, int[] v, int bag) {
-		return process(w, v, 0, 0, bag);
-	}
-
-	// 不变 ： w[]  v[]  bag
-	// index... 最大价值
-	// 0..index-1上做了货物的选择，使得你已经达到的重量是多少alreadyW
-	// 如果返回-1，认为没有方案
-	// 如果不返回-1，认为返回的值是真实价值
-	public static int process(int[] w, int[] v, int index, int alreadyW, int bag) {
-		if (alreadyW > bag) {
-			return -1;
-		}
-		// 重量没超
-		if (index == w.length) {
-			return 0;
-		}
-		int p1 = process(w, v, index + 1, alreadyW, bag);
-		int p2next = process(w, v, index + 1, alreadyW + w[index], bag);
-		int p2 = -1;
-		if (p2next != -1) {
-			p2 = v[index] + p2next;
-		}
-		return Math.max(p1, p2);
-
-	}
-
-	public static int maxValue(int[] w, int[] v, int bag) {
-		return process(w, v, 0, bag);
-	}
-
-	// 只剩下rest的空间了，
-	// index...货物自由选择，但是剩余空间不要小于0
-	// 返回 index...货物能够获得的最大价值
-	public static int process(int[] w, int[] v, int index, int rest) {
-		if (rest < 0) { // base case 1
-			return -1;
-		}
-		// rest >=0
-		if (index == w.length) { // base case 2
-			return 0;
-		}
-		// 有货也有空间
-		int p1 = process(w, v, index + 1, rest);
-		int p2 = -1;
-		int p2Next = process(w, v, index + 1, rest - w[index]);
-		if(p2Next!=-1) {
-			p2 = v[index] + p2Next;
-		}
-		return Math.max(p1, p2);
-	}
-
-	public static int dpWay(int[] w, int[] v, int bag) {
-		int N = w.length;
-		int[][] dp = new int[N + 1][bag + 1];
-		for (int index = N - 1; index >= 0; index--) {
-			for (int rest = 1; rest <= bag; rest++) {
-				dp[index][rest] = dp[index + 1][rest];
-				if (rest >= w[index]) {
-					dp[index][rest] = Math.max(dp[index][rest], v[index] + dp[index + 1][rest - w[index]]);
-				}
-			}
-		}
-		return dp[0][bag];
-	}
-
-	public static void main(String[] args) {
-		int[] weights = { 3, 2, 4, 7 };
-		int[] values = { 5, 6, 3, 19 };
-		int bag = 11;
-		System.out.println(maxValue(weights, values, bag));
-		System.out.println(dpWay(weights, values, bag));
-	}
-
-}

src/class11_17/Code08_CardsInLine.java

@@ -1,82 +0,0 @@
-package class11_17;
-
-public class Code08_CardsInLine {
-
-	public static int win1(int[] arr) {
-		if (arr == null || arr.length == 0) {
-			return 0;
-		}
-		return Math.max(
-				f(arr, 0, arr.length - 1),
-				s(arr, 0, arr.length - 1)
-				);
-	}
-
-	// L....R
-	// F  S  L+1..R
-	         // L..R-1
-	public static int f(int[] arr, int L, int R) {
-		if (L == R) {
-			return arr[L];
-		}
-		
-		return Math.max(
-				arr[L] + s(arr, L + 1, R),
-				arr[R] + s(arr, L, R - 1)
-				);
-	}
-
-	// arr[L..R]
-	public static int s(int[] arr, int L, int R) {
-		if (L == R) {
-			return 0;
-		}
-		return Math.min(
-				f(arr, L + 1, R), // arr[i]
-				f(arr, L, R - 1)  // arr[j]
-				);
-	}
-
-	public static int win2(int[] arr) {
-		if (arr == null || arr.length == 0) {
-			return 0;
-		}
-		int N = arr.length;
-		int[][] f = new int[N][N];
-		int[][] s = new int[N][N];
-		for(int i = 0; i < N;i++) {
-			f[i][i] = arr[i];
-		}
-		// s[i][i] = 0;
-		for(int i = 1; i < N;i++) {
-			int L =0;
-			int R =i;
-			while(L < N && R < N) {
-				
-				f[L][R] = Math.max(
-						arr[L] + s[L + 1][ R],
-						arr[R] + s[L][R - 1]
-						); 
-				s[L][R] = Math.min(
-						f[L + 1][R], // arr[i]
-						f[L][R - 1]  // arr[j]
-						); 
-				
-				L++;
-				R++;
-				
-			}
-		}
-		return Math.max(f[0][N-1], s[0][N-1]);
-	}
-
-	public static void main(String[] args) {
-		int[] arr = { 4,7,9,5,19,29,80,4 };
-		// A 4 9
-		// B 7 5
-		System.out.println(win1(arr));
-		System.out.println(win2(arr));
-
-	}
-
-}

src/class12/Code01_IsCBT.java

@@ -1,4 +1,4 @@
-package class08_12;
+package class12;
 
 import java.util.LinkedList;
 

src/class12/Code01_RobotWalk.java

@@ -1,191 +0,0 @@
-package class12;
-
-public class Code01_RobotWalk {
-
-	public static int ways1(int N, int M, int K, int P) {
-		// 参数无效直接返回0
-		if (N < 2 || K < 1 || M < 1 || M > N || P < 1 || P > N) {
-			return 0;
-		}
-		// 总共N个位置，从M点出发，还剩K步，返回最终能达到P的方法数
-		return walk(N, M, K, P);
-	}
-
-	// N : 位置为1 ~ N，固定参数
-	// cur : 当前在cur位置，可变参数
-	// rest : 还剩res步没有走，可变参数
-	// P : 最终目标位置是P，固定参数
-	// 该函数的含义：只能在1~N这些位置上移动，当前在cur位置，走完rest步之后，停在P位置的方法数作为返回值返回
-	public static int walk(int N, int cur, int rest, int P) {
-		// 如果没有剩余步数了，当前的cur位置就是最后的位置
-		// 如果最后的位置停在P上，那么之前做的移动是有效的
-		// 如果最后的位置没在P上，那么之前做的移动是无效的
-		if (rest == 0) {
-			return cur == P ? 1 : 0;
-		}
-		// 如果还有rest步要走，而当前的cur位置在1位置上，那么当前这步只能从1走向2
-		// 后续的过程就是，来到2位置上，还剩rest-1步要走
-		if (cur == 1) {
-			return walk(N, 2, rest - 1, P);
-		}
-		// 如果还有rest步要走，而当前的cur位置在N位置上，那么当前这步只能从N走向N-1
-		// 后续的过程就是，来到N-1位置上，还剩rest-1步要走
-		if (cur == N) {
-			return walk(N, N - 1, rest - 1, P);
-		}
-		// 如果还有rest步要走，而当前的cur位置在中间位置上，那么当前这步可以走向左，也可以走向右
-		// 走向左之后，后续的过程就是，来到cur-1位置上，还剩rest-1步要走
-		// 走向右之后，后续的过程就是，来到cur+1位置上，还剩rest-1步要走
-		// 走向左、走向右是截然不同的方法，所以总方法数要都算上
-		return walk(N, cur + 1, rest - 1, P) + walk(N, cur - 1, rest - 1, P);
-	}
-	
-	
-	
-	
-	
-	
-	public static int waysCache(int N, int M, int K, int P) {
-		// 参数无效直接返回0
-		if (N < 2 || K < 1 || M < 1 || M > N || P < 1 || P > N) {
-			return 0;
-		}
-		
-		int[][] dp = new int[N+1][K+1];
-		for(int row = 0; row <= N; row++) {
-			for(int col = 0; col <= K; col++) {
-				dp[row][col] = -1;
-			}
-		}
-		return walkCache(N, M, K, P,dp);
-	}
-
-	// HashMap<String, Integer>   (19,100)  "19_100"
-	// 我想把所有cur和rest的组合，返回的结果，加入到缓存里
-	public static int walkCache(int N, int cur, int rest, int P, int[][] dp) {
-		if(dp[cur][rest] != -1) {
-			return dp[cur][rest];
-		}
-		if (rest == 0) {
-			dp[cur][rest] = cur == P ? 1 : 0;
-			return dp[cur][rest];
-		}
-		if (cur == 1) {
-			dp[cur][rest] = walkCache(N, 2, rest - 1, P, dp);
-			return dp[cur][rest];
-		}
-		if (cur == N) {
-			dp[cur][rest] =walkCache(N, N - 1, rest - 1, P,dp);
-			return dp[cur][rest];
-		}
-		dp[cur][rest] = walkCache(N, cur + 1, rest - 1, P,dp) 
-				+ walkCache(N, cur - 1, rest - 1, P, dp);
-		return dp[cur][rest];
-	}
-	
-	
-	
-	
-	
-	
-	
-	
-	
-
-	public static int ways2(int N, int M, int K, int P) {
-		// 参数无效直接返回0
-		if (N < 2 || K < 1 || M < 1 || M > N || P < 1 || P > N) {
-			return 0;
-		}
-		int[][] dp = new int[K + 1][N + 1];
-		dp[0][P] = 1;
-		for (int i = 1; i <= K; i++) {
-			for (int j = 1; j <= N; j++) {
-				if (j == 1) {
-					dp[i][j] = dp[i - 1][2];
-				} else if (j == N) {
-					dp[i][j] = dp[i - 1][N - 1];
-				} else {
-					dp[i][j] = dp[i - 1][j - 1] + dp[i - 1][j + 1];
-				}
-			}
-		}
-		return dp[K][M];
-	}
-
-	public static int ways3(int N, int M, int K, int P) {
-		// 参数无效直接返回0
-		if (N < 2 || K < 1 || M < 1 || M > N || P < 1 || P > N) {
-			return 0;
-		}
-		int[] dp = new int[N + 1];
-		dp[P] = 1;
-		for (int i = 1; i <= K; i++) {
-			int leftUp = dp[1];// 左上角的值
-			for (int j = 1; j <= N; j++) {
-				int tmp = dp[j];
-				if (j == 1) {
-					dp[j] = dp[j + 1];
-				} else if (j == N) {
-					dp[j] = leftUp;
-				} else {
-					dp[j] = leftUp + dp[j + 1];
-				}
-				leftUp = tmp;
-			}
-		}
-		return dp[M];
-	}
-
-	// ways4是你的方法
-	public static int ways4(int N, int M, int K, int P) {
-		if (N < 2 || K < 1 || M < 1 || M > N || P < 1 || P > N) {
-			return 0;
-		}
-		return process(N, 0, P, M, K);
-	}
-
-	// 一共N个位置，从M点出发，一共只有K步。返回走到位置j，剩余步数为i的方法数
-	public static int process(int N, int i, int j, int M, int K) {
-		if (i == K) {
-			return j == M ? 1 : 0;
-		}
-		if (j == 1) {
-			return process(N, i + 1, j + 1, M, K);
-		}
-		if (j == N) {
-			return process(N, i + 1, j - 1, M, K);
-		}
-		return process(N, i + 1, j + 1, M, K) + process(N, i + 1, j - 1, M, K);
-	}
-
-	// ways5是你的方法的dp优化
-	public static int ways5(int N, int M, int K, int P) {
-		if (N < 2 || K < 1 || M < 1 || M > N || P < 1 || P > N) {
-			return 0;
-		}
-		int[][] dp = new int[K + 1][N + 1];
-		dp[K][M] = 1;
-		for (int i = K - 1; i >= 0; i--) {
-			for (int j = 1; j <= N; j++) {
-				if (j == 1) {
-					dp[i][j] = dp[i + 1][j + 1];
-				} else if (j == N) {
-					dp[i][j] = dp[i + 1][j - 1];
-				} else {
-					dp[i][j] = dp[i + 1][j + 1] + dp[i + 1][j - 1];
-				}
-			}
-		}
-		return dp[0][P];
-	}
-
-	public static void main(String[] args) {
-		System.out.println(ways1(7, 4, 9, 5));
-		System.out.println(ways2(7, 4, 9, 5));
-		System.out.println(ways3(7, 4, 9, 5));
-		System.out.println(ways4(7, 4, 9, 5));
-		System.out.println(ways5(7, 4, 9, 5));
-	}
-
-}

src/class12/Code02_IsBST.java

@@ -1,4 +1,4 @@
-package class08_12;
+package class12;
 
 import java.util.ArrayList;
 

src/class12/Code02_StickersToSpellWord.java

@@ -1,152 +0,0 @@
-package class12;
-
-import java.util.Arrays;
-import java.util.HashMap;
-
-public class Code02_StickersToSpellWord {
-
-	public static int minStickers1(String[] stickers, String target) {
-		
-		int n = stickers.length;
-		
-		int[][] map = new int[n][26];// stickers -> [26] [26] [26]
-		for (int i = 0; i < n; i++) {
-			char[] str = stickers[i].toCharArray();
-			for (char c : str) {
-				map[i][c - 'a']++;
-			}
-		}
-		HashMap<String, Integer> dp = new HashMap<>();
-		dp.put("", 0);
-		return process1(dp, map, target);
-	}
-
-	// dp 傻缓存，如果t已经算过了，直接返回dp中的值
-	// t 剩余的目标
-	// 0..N每一个字符串所含字符的词频统计
-	// 返回值是-1，map 中的贴纸  怎么都无法rest
-	public static int process1(
-			HashMap<String, Integer> dp,
-			int[][] map, 
-			String rest) {
-		if (dp.containsKey(rest)) {
-			return dp.get(rest);
-		}
-		// 以下就是正式的递归调用过程
-		int ans = Integer.MAX_VALUE; // ans -> 搞定rest，使用的最少的贴纸数量 
-		int n = map.length; // N种贴纸
-		int[] tmap = new int[26]; // tmap 去替代 rest
-		char[] target = rest.toCharArray();
-		for (char c : target) {
-			tmap[c - 'a']++;
-		}
-		for (int i = 0; i < n; i++) {
-			// 枚举当前第一张贴纸是谁？
-			if (map[i][target[0] - 'a'] == 0) {
-				continue;
-			}
-			StringBuilder sb = new StringBuilder();
-			// i 贴纸， j 枚举a~z字符
-			for (int j = 0; j < 26; j++) { // 
-				if (tmap[j] > 0) { // j这个字符是target需要的
-					for (int k = 0; k < Math.max(0, tmap[j] - map[i][j]); k++) {
-						sb.append((char) ('a' + j));
-					}
-				}
-			}
-			// sb ->  i
-			String s = sb.toString();
-			int tmp = process1(dp, map, s);
-			if (tmp != -1) {
-				ans = Math.min(ans, 1 + tmp);
-			}
-		}
-		// ans 系统最大  rest
-		dp.put(rest, ans == Integer.MAX_VALUE ? -1 : ans);
-		return dp.get(rest);
-	}
-
-	public static int minStickers2(String[] stickers, String target) {
-		int n = stickers.length;
-		int[][] map = new int[n][26];
-		for (int i = 0; i < n; i++) {
-			char[] str = stickers[i].toCharArray();
-			for (char c : str) {
-				map[i][c - 'a']++;
-			}
-		}
-		char[] str = target.toCharArray();
-		int[] tmap = new int[26];
-		for (char c : str) {
-			tmap[c - 'a']++;
-		}
-		HashMap<String, Integer> dp = new HashMap<>();
-		int ans = process2(map, 0, tmap, dp);
-		return ans;
-	}
-
-	public static int process2(int[][] map, int i, int[] tmap, HashMap<String, Integer> dp) {
-		StringBuilder keyBuilder = new StringBuilder();
-		keyBuilder.append(i + "_");
-		for (int asc = 0; asc < 26; asc++) {
-			if (tmap[asc] != 0) {
-				keyBuilder.append((char) (asc + 'a') + "_" + tmap[asc] + "_");
-			}
-		}
-		String key = keyBuilder.toString();
-		if (dp.containsKey(key)) {
-			return dp.get(key);
-		}
-		boolean finish = true;
-		for (int asc = 0; asc < 26; asc++) {
-			if (tmap[asc] != 0) {
-				finish = false;
-				break;
-			}
-		}
-		if (finish) {
-			dp.put(key, 0);
-			return 0;
-		}
-		if (i == map.length) {
-			dp.put(key, -1);
-			return -1;
-		}
-		int maxZhang = 0;
-		for (int asc = 0; asc < 26; asc++) {
-			if (map[i][asc] != 0 && tmap[asc] != 0) {
-				maxZhang = Math.max(maxZhang, (tmap[asc] / map[i][asc]) + (tmap[asc] % map[i][asc] == 0 ? 0 : 1));
-			}
-		}
-		int[] backup = Arrays.copyOf(tmap, tmap.length);
-		int min = Integer.MAX_VALUE;
-		int next = process2(map, i + 1, tmap, dp);
-		tmap = Arrays.copyOf(backup, backup.length);
-		if (next != -1) {
-			min = next;
-		}
-		for (int zhang = 1; zhang <= maxZhang; zhang++) {
-			for (int asc = 0; asc < 26; asc++) {
-				tmap[asc] = Math.max(0, tmap[asc] - (map[i][asc] * zhang));
-			}
-			next = process2(map, i + 1, tmap, dp);
-			tmap = Arrays.copyOf(backup, backup.length);
-			if (next != -1) {
-				min = Math.min(min, zhang + next);
-			}
-		}
-		int ans = min == Integer.MAX_VALUE ? -1 : min;
-		dp.put(key, ans);
-		return ans;
-	}
-	
-	public static void main(String[] args) {
-		String[] arr = {"aaaa","bbaa","ccddd"};
-		String str = "abcccccdddddbbbaaaaa";
-		System.out.println(minStickers1(arr, str));
-		System.out.println(minStickers2(arr, str));
-		
-		
-	}
-
-}

src/class12/Code03_IsBalanced.java

@@ -1,4 +1,4 @@
-package class08_12;
+package class12;
 
 public class Code03_IsBalanced {
 

src/class12/Code04_CardsInLine.java

@@ -1,61 +0,0 @@
-package class12;
-
-public class Code04_CardsInLine {
-
-	public static int win1(int[] arr) {
-		if (arr == null || arr.length == 0) {
-			return 0;
-		}
-		return Math.max(f(arr, 0, arr.length - 1), s(arr, 0, arr.length - 1));
-	}
-
-	public static int f(int[] arr, int L, int R) {
-		if (L == R) {
-			return arr[L];
-		}
-		return Math.max(arr[L] + s(arr, L + 1, R), arr[R] + s(arr, L, R - 1));
-	}
-
-	public static int s(int[] arr, int L, int R) {
-		if (L == R) {
-			return 0;
-		}
-		return Math.min(f(arr, L + 1, R), f(arr, L, R - 1));
-	}
-
-	public static int windp(int[] arr) {
-		if (arr == null || arr.length == 0) {
-			return 0;
-		}
-		int N = arr.length;
-		int[][] f = new int[N][N];
-		int[][] s = new int[N][N];
-		for (int i = 0; i < N; i++) {
-			f[i][i] = arr[i];
-		}
-		// 0,0 右下方移动
-		// 0,1
-		// 0,2
-		// 0,N-1
-		for (int col = 1; col < N; col++) {
-			// 对角线出发位置(0,col)
-			int L = 0;
-			int R = col;
-			while (L < N && R < N) {
-				f[L][R] = Math.max(arr[L] + s[L + 1][R], arr[R] + s[L][R - 1]);
-				s[L][R] = Math.min(f[L + 1][R], f[L][R - 1]);
-				L++;
-				R++;
-			}
-		}
-		return Math.max(f[0][N - 1], s[0][N - 1]);
-	}
-
-	public static void main(String[] args) {
-		int[] arr = { 5, 7, 4, 5, 8, 1, 6, 0, 3, 4, 6, 1, 7 };
-		System.out.println(win1(arr));
-		System.out.println(windp(arr));
-
-	}
-
-}

src/class12/Code04_IsFull.java

@@ -1,4 +1,4 @@
-package class08_12;
+package class12;
 
 public class Code04_IsFull {
 

src/class12/Code05_MaxSubBSTSize.java

@@ -1,4 +1,4 @@
-package class08_12;
+package class12;
 
 import java.util.ArrayList;
 

src/class12/Code05_PalindromeSubsequence.java

@@ -1,38 +0,0 @@
-package class12;
-
-public class Code05_PalindromeSubsequence {
-
-	public static int lcse(char[] str1, char[] str2) {
-		
-		
-		
-		
-		int[][] dp = new int[str1.length][str2.length];
-		
-		
-		
-		dp[0][0] = str1[0] == str2[0] ? 1 : 0;
-		
-		
-		for (int i = 1; i < str1.length; i++) {
-			dp[i][0] = Math.max(dp[i - 1][0], str1[i] == str2[0] ? 1 : 0);
-		}
-		for (int j = 1; j < str2.length; j++) {
-			dp[0][j] = Math.max(dp[0][j - 1], str1[0] == str2[j] ? 1 : 0);
-		}
-		for (int i = 1; i < str1.length; i++) {
-			for (int j = 1; j < str2.length; j++) {
-				dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]);
-				if (str1[i] == str2[j]) {
-					dp[i][j] = Math.max(dp[i][j], dp[i - 1][j - 1] + 1);
-				} 
-			}
-		}
-		return dp[str1.length - 1][str2.length - 1];
-	}
-
-	public static void main(String[] args) {
-
-	}
-
-}

src/class12/Code06_MaxDistance.java

@@ -1,4 +1,4 @@
-package class08_12;
+package class12;
 
 import java.util.ArrayList;
 import java.util.HashMap;

src/class12/Code09_CoinsWay.java

@@ -1,106 +0,0 @@
-package class12;
-
-public class Code09_CoinsWay {
-
-	// arr中都是正数且无重复值，返回组成aim的方法数
-	public static int ways1(int[] arr, int aim) {
-		if (arr == null || arr.length == 0 || aim < 0) {
-			return 0;
-		}
-		return process1(arr, 0, aim);
-	}
-
-	public static int process1(int[] arr, int index, int rest) {
-		if(index == arr.length) {
-			return rest == 0 ? 1 : 0 ;	
-		}
-		int ways = 0;
-		for(int zhang = 0;  zhang * arr[index] <= rest ;zhang++) {
-			ways += process1(arr, index + 1, rest -  (zhang * arr[index])  );
-		}
-		return ways;
-	}
-
-	public static int ways2(int[] arr, int aim) {
-		if (arr == null || arr.length == 0 || aim < 0) {
-			return 0;
-		}
-		int[][] dp = new int[arr.length+1][aim+1];
-		// 一开始所有的过程，都没有计算呢
-		// dp[..][..]  = -1
-		for(int i = 0 ; i < dp.length; i++) {
-			for(int j = 0 ; j < dp[0].length; j++) {
-				dp[i][j] = -1;
-			}
-		}
-		return process2(arr, 0, aim , dp);
-	}
-	
-	// 如果index和rest的参数组合，是没算过的，dp[index][rest] == -1
-	// 如果index和rest的参数组合，是算过的，dp[index][rest]  > - 1
-	public static int process2(int[] arr, 
-			int index, int rest,
-			int[][] dp) {
-		if(dp[index][rest] != -1) {
-			return dp[index][rest];
-		}
-		if(index == arr.length) {
-			dp[index][rest] = rest == 0 ? 1 :0;
-			return  dp[index][rest];	
-		}
-		int ways = 0;
-		for(int zhang = 0;  zhang * arr[index] <= rest ;zhang++) {
-			ways += process2(arr, index + 1, rest -  (zhang * arr[index]) , dp );
-		}
-		dp[index][rest] = ways;
-		return ways;
-	}
-	
-	public static int ways3(int[] arr, int aim) {
-		if (arr == null || arr.length == 0 || aim < 0) {
-			return 0;
-		}
-		int N = arr.length;
-		int[][] dp = new int[N + 1][aim + 1];
-		dp[N][0] = 1;// dp[N][1...aim] = 0;
-		for(int index = N - 1; index >= 0; index--) {
-			for(int rest = 0; rest <= aim; rest++) {
-				int ways = 0;
-				for(int zhang = 0;  zhang * arr[index] <= rest ;zhang++) {
-					ways += dp[index + 1] [rest -  (zhang * arr[index])];
-				}
-				dp[index][rest] = ways;
-			}
-		}
-		return dp[0][aim];
-	}
-	
-	public static int ways4(int[] arr, int aim) {
-		if (arr == null || arr.length == 0 || aim < 0) {
-			return 0;
-		}
-		int N = arr.length;
-		int[][] dp = new int[N + 1][aim + 1];
-		dp[N][0] = 1;// dp[N][1...aim] = 0;
-		for(int index = N - 1; index >= 0; index--) {
-			for(int rest = 0; rest <= aim; rest++) {
-				dp[index][rest] = dp[index+1][rest];
-				if(rest - arr[index] >= 0) {
-					dp[index][rest] += dp[index][rest - arr[index]];
-				}
-			}
-		}
-		return dp[0][aim];
-	}
-	
-
-	public static void main(String[] args) {
-		int[] arr = { 5, 10,50,100 };
-		int sum = 1000;
-		System.out.println(ways1(arr, sum));
-		System.out.println(ways2(arr, sum));
-		System.out.println(ways3(arr, sum));
-		System.out.println(ways4(arr, sum));
-	}
-
-}

src/class13/Code01_IsCBT.java

@@ -1,4 +1,4 @@
-package class08_13;
+package class13;
 
 import java.util.LinkedList;
 

src/class13/Code02_MaxSubBSTHead.java

@@ -1,4 +1,4 @@
-package class08_13;
+package class13;
 
 import java.util.ArrayList;
 

src/class13/Code03_lowestAncestor.java

@@ -1,4 +1,4 @@
-package class08_13;
+package class13;
 
 import java.util.ArrayList;
 import java.util.HashMap;

src/class13/Code04_MaxHappy.java

@@ -1,4 +1,4 @@
-package class08_13;
+package class13;
 
 import java.util.ArrayList;
 import java.util.List;

src/class13/Code05_LowestLexicography.java

@@ -1,10 +1,10 @@
-package class09_13;
+package class13;
 
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.TreeSet;
 
-public class Code01_LowestLexicography {
+public class Code05_LowestLexicography {
 
 	public static String lowestString1(String[] strs) {
 		if (strs == null || strs.length == 0) {

src/class14/Code01_Light.java

@@ -1,4 +1,4 @@
-package class09_14;
+package class14;
 
 import java.util.HashSet;
 

src/class14/Code02_LessMoneySplitGold.java

@@ -1,4 +1,4 @@
-package class09_14;
+package class14;
 
 import java.util.PriorityQueue;
 

src/class14/Code03_BestArrange.java

@@ -1,4 +1,4 @@
-package class09_14;
+package class14;
 
 import java.util.Arrays;
 import java.util.Comparator;

src/class14/Code04_IPO.java

@@ -1,4 +1,4 @@
-package class09_14;
+package class14;
 
 import java.util.Comparator;
 import java.util.PriorityQueue;

src/class14/Code05_UnionFind.java

@@ -1,4 +1,4 @@
-package class09_14;
+package class14;
 
 import java.util.HashMap;
 import java.util.List;

src/class15/Code01_FriendCircles.java

@@ -1,4 +1,4 @@
-package class09_15;
+package class15;
 
 // 本题为leetcode原题
 // 测试链接：https://leetcode.com/problems/friend-circles/

src/class15/Code02_NumberOfIslands.java

@@ -1,4 +1,4 @@
-package class09_15;
+package class15;
 
 import java.util.ArrayList;
 import java.util.HashMap;

src/class15/Code03_NumberOfIslandsII.java

@@ -1,4 +1,4 @@
-package class09_15;
+package class15;
 
 import java.util.ArrayList;
 import java.util.HashMap;

src/class16/Code01_BFS.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 import java.util.HashSet;
 import java.util.LinkedList;

src/class16/Code02_DFS.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 import java.util.HashSet;
 import java.util.Stack;

src/class16/Code03_TopologicalOrderBFS.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 import java.util.ArrayList;
 import java.util.HashMap;

src/class16/Code03_TopologicalOrderDFS1.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 import java.util.ArrayList;
 import java.util.Comparator;

src/class16/Code03_TopologicalOrderDFS2.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 import java.util.ArrayList;
 import java.util.Comparator;

src/class16/Code03_TopologySort.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 import java.util.ArrayList;
 import java.util.HashMap;

src/class16/Code04_Kruskal.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 import java.util.Collection;
 import java.util.Comparator;

src/class16/Code05_Prim.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 import java.util.Comparator;
 import java.util.HashSet;

src/class16/Code06_Dijkstra.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 import java.util.HashMap;
 import java.util.HashSet;

src/class16/Edge.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 public class Edge {
 	public int weight;

src/class16/Graph.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 import java.util.HashMap;
 import java.util.HashSet;

src/class16/GraphGenerator.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class16;
 
 public class GraphGenerator {
 

src/class16/Node.java

@@ -1,4 +1,4 @@
-package class10_17;
+package class16;
 
 import java.util.ArrayList;
 

src/class17/Code01_Dijkstra.java

@@ -1,4 +1,4 @@
-package class10_17;
+package class17;
 
 import java.util.HashMap;
 import java.util.HashSet;
@@ -14,7 +14,7 @@ public class Code01_Dijkstra {
 		HashSet<Node> selectedNodes = new HashSet<>();
 		Node minNode = getMinDistanceAndUnselectedNode(distanceMap, selectedNodes);
 		while (minNode != null) {
-			//  原始点  ->  minNode(跳转点)   最小距离distance
+			// 原始点 -> minNode(跳转点) 最小距离distance
 			int distance = distanceMap.get(minNode);
 			for (Edge edge : minNode.edges) {
 				Node toNode = edge.to;
@@ -55,12 +55,13 @@ public class Code01_Dijkstra {
 	}
 
 	public static class NodeHeap {
-		private Node[] nodes; // 实际的堆结构
-		// key 某一个node， value 上面堆中的位置
+		// 堆！
+		private Node[] nodes;
+		// node -> 堆上的什么位置？
+		
 		private HashMap<Node, Integer> heapIndexMap;
-		// key 某一个节点， value 从源节点出发到该节点的目前最小距离
 		private HashMap<Node, Integer> distanceMap;
-		private int size; // 堆上有多少个点
+		private int size;
 
 		public NodeHeap(int size) {
 			nodes = new Node[size];
@@ -76,21 +77,22 @@ public class Code01_Dijkstra {
 		// 有一个点叫node，现在发现了一个从源节点出发到达node的距离为distance
 		// 判断要不要更新，如果需要的话，就更新
 		public void addOrUpdateOrIgnore(Node node, int distance) {
-			if (inHeap(node)) {
+			if (inHeap(node)) { // update
 				distanceMap.put(node, Math.min(distanceMap.get(node), distance));
 				insertHeapify(node, heapIndexMap.get(node));
 			}
-			if (!isEntered(node)) {
+			if (!isEntered(node)) { // add
 				nodes[size] = node;
 				heapIndexMap.put(node, size);
 				distanceMap.put(node, distance);
 				insertHeapify(node, size++);
 			}
+			// ignore
 		}
 
 		public NodeRecord pop() {
 			NodeRecord nodeRecord = new NodeRecord(nodes[0], distanceMap.get(nodes[0]));
-			swap(0, size - 1);
+			swap(0, size - 1); // 0 > size - 1    size - 1 > 0
 			heapIndexMap.put(nodes[size - 1], -1);
 			distanceMap.remove(nodes[size - 1]);
 			// free C++同学还要把原本堆顶节点析构，对java同学不必

src/class17/Code02_Hanoi.java

@@ -1,8 +1,8 @@
-package class11_17;
+package class17;
 
 import java.util.Stack;
 
-public class Code01_Hanoi {
+public class Code02_Hanoi {
 
 	public static void hanoi1(int n) {
 		leftToRight(n);
@@ -10,7 +10,7 @@ public class Code01_Hanoi {
 
 	// 请把1~N层圆盘 从左 -> 右
 	public static void leftToRight(int n) {
-		if (n == 1) {
+		if (n == 1) { // base case
 			System.out.println("Move 1 from left to right");
 			return;
 		}
@@ -76,7 +76,6 @@ public class Code01_Hanoi {
 		}
 	}
 
-	// 1~i 圆盘 目标是from -> to， other是另外一个
 	public static void func(int N, String from, String to, String other) {
 		if (N == 1) { // base
 			System.out.println("Move 1 from " + from + " to " + to);
@@ -133,8 +132,8 @@ public class Code01_Hanoi {
 		hanoi1(n);
 		System.out.println("============");
 		hanoi2(n);
-		System.out.println("============");
-		hanoi3(n);
+//		System.out.println("============");
+//		hanoi3(n);
 	}
 
 }

src/class17/Code03_PrintAllSubsquences.java

@@ -1,11 +1,12 @@
-package class11_17;
+package class17;
 
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
 
-public class Code02_PrintAllSubsquences {
+public class Code03_PrintAllSubsquences {
 
+	// s -> "abc" ->
 	public static List<String> subs(String s) {
 		char[] str = s.toCharArray();
 		String path = "";
@@ -14,19 +15,21 @@ public class Code02_PrintAllSubsquences {
 		return ans;
 	}
 
-	// str固定，不变
-	// index此时来到的位置, 要  or 不要
-	// 如果index来到了str中的终止位置，把沿途路径所形成的答案，放入ans中
-	// 之前做出的选择，就是path
+	// str 固定参数
+	// 来到了str[index]字符，index是位置
+	// str[0..index-1]已经走过了！之前的决定，都在path上
+	// 之前的决定已经不能改变了，就是path
+	// str[index....]还能决定，之前已经确定，而后面还能自由选择的话，
+	// 把所有生成的子序列，放入到ans里去
 	public static void process1(char[] str, int index, List<String> ans, String path) {
 		if (index == str.length) {
 			ans.add(path);
 			return;
 		}
-		String no = path;
-		process1(str, index + 1, ans, no);
-		String yes = path + String.valueOf(str[index]);
-		process1(str, index + 1, ans, yes);
+		// 没有要index位置的字符
+		process1(str, index + 1, ans, path);
+		// 要了index位置的字符
+		process1(str, index + 1, ans, path + String.valueOf(str[index]));
 	}
 
 	public static List<String> subsNoRepeat(String s) {
@@ -41,9 +44,7 @@ public class Code02_PrintAllSubsquences {
 		return ans;
 	}
 
-	// str  index  set
-	public static void process2(char[] str, int index,
-			HashSet<String> set, String path) {
+	public static void process2(char[] str, int index, HashSet<String> set, String path) {
 		if (index == str.length) {
 			set.add(path);
 			return;
@@ -55,7 +56,7 @@ public class Code02_PrintAllSubsquences {
 	}
 
 	public static void main(String[] args) {
-		String test = "aacc";
+		String test = "acccc";
 		List<String> ans1 = subs(test);
 		List<String> ans2 = subsNoRepeat(test);
 

src/class17/Code04_PrintAllPermutations.java

@@ -0,0 +1,110 @@
+package class17;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Code04_PrintAllPermutations {
+
+	public static List<String> permutation1(String s) {
+		List<String> ans = new ArrayList<>();
+		if (s == null || s.length() == 0) {
+			return ans;
+		}
+		char[] str = s.toCharArray();
+		ArrayList<Character> rest = new ArrayList<Character>();
+		for (char cha : str) {
+			rest.add(cha);
+		}
+		String path = "";
+		f(rest, path, ans);
+		return ans;
+	}
+
+	public static void f(ArrayList<Character> rest, String path, List<String> ans) {
+		if (rest.isEmpty()) {
+			ans.add(path);
+		} else {
+			int N = rest.size();
+			for (int i = 0; i < N; i++) {
+				char cur = rest.get(i);
+				rest.remove(i);
+				f(rest, path + cur, ans);
+				rest.add(i, cur);
+			}
+		}
+	}
+
+	public static List<String> permutation2(String s) {
+		List<String> ans = new ArrayList<>();
+		if (s == null || s.length() == 0) {
+			return ans;
+		}
+		char[] str = s.toCharArray();
+		g1(str, 0, ans);
+		return ans;
+	}
+
+	public static void g1(char[] str, int index, List<String> ans) {
+		if (index == str.length) {
+			ans.add(String.valueOf(str));
+		} else {
+			for (int i = index; i < str.length; i++) {
+				swap(str, index, i);
+				g1(str, index + 1, ans);
+				swap(str, index, i);
+			}
+		}
+	}
+
+	public static List<String> permutation3(String s) {
+		List<String> ans = new ArrayList<>();
+		if (s == null || s.length() == 0) {
+			return ans;
+		}
+		char[] str = s.toCharArray();
+		g2(str, 0, ans);
+		return ans;
+	}
+
+	public static void g2(char[] str, int index, List<String> ans) {
+		if (index == str.length) {
+			ans.add(String.valueOf(str));
+		} else {
+			boolean[] visited = new boolean[256];
+			for (int i = index; i < str.length; i++) {
+				if (!visited[str[i]]) {
+					visited[str[i]] = true;
+					swap(str, index, i);
+					g2(str, index + 1, ans);
+					swap(str, index, i);
+				}
+			}
+		}
+	}
+
+	public static void swap(char[] chs, int i, int j) {
+		char tmp = chs[i];
+		chs[i] = chs[j];
+		chs[j] = tmp;
+	}
+
+	public static void main(String[] args) {
+		String s = "acc";
+		List<String> ans1 = permutation1(s);
+		for (String str : ans1) {
+			System.out.println(str);
+		}
+		System.out.println("=======");
+		List<String> ans2 = permutation2(s);
+		for (String str : ans2) {
+			System.out.println(str);
+		}
+		System.out.println("=======");
+		List<String> ans3 = permutation3(s);
+		for (String str : ans3) {
+			System.out.println(str);
+		}
+
+	}
+
+}

src/class17/Code05_ReverseStackUsingRecursive.java

@@ -1,8 +1,8 @@
-package class11_17;
+package class17;
 
 import java.util.Stack;
 
-public class Code04_ReverseStackUsingRecursive {
+public class Code05_ReverseStackUsingRecursive {
 
 	public static void reverse(Stack<Integer> stack) {
 		if (stack.isEmpty()) {
@@ -13,6 +13,9 @@ public class Code04_ReverseStackUsingRecursive {
 		stack.push(i);
 	}
 
+	// 栈底元素移除掉
+	// 上面的元素盖下来
+	// 返回移除掉的栈底元素
 	public static int f(Stack<Integer> stack) {
 		int result = stack.pop();
 		if (stack.isEmpty()) {

src/class17/Edge.java

@@ -1,4 +1,4 @@
-package class10_17;
+package class17;
 
 public class Edge {
 	public int weight;

src/class17/Graph.java

@@ -1,4 +1,4 @@
-package class10_17;
+package class17;
 
 import java.util.HashMap;
 import java.util.HashSet;

src/class17/Node.java

@@ -1,4 +1,4 @@
-package class10_16;
+package class17;
 
 import java.util.ArrayList;