Merge branch 'youngyangyang04:master' into master

Author: xllpiupiu

problems/0024.两两交换链表中的节点.md

@@ -131,6 +131,27 @@ class Solution {
 Python：
 
 Go：
+```go
+func swapPairs(head *ListNode) *ListNode {
+    dummy := &ListNode{
+        Next: head,
+    }
+    //head=list[i]
+    //pre=list[i-1]
+    pre := dummy 
+    for head != nil && head.Next != nil {
+        pre.Next = head.Next
+        next := head.Next.Next
+        head.Next.Next = head
+        head.Next = next
+        //pre=list[(i+2)-1]
+        pre = head 
+        //head=list[(i+2)]
+        head = next
+    }
+    return dummy.Next
+}
+```
 
 Javascript:
 ```javascript

problems/0037.解数独.md

@@ -291,7 +291,61 @@ Python：
 
 Go：
 
+Javascript:
+```Javascript
+var solveSudoku = function(board) {
+    function isValid(row, col, val, board) {
+        let len = board.length
+        // 行不能重复
+        for(let i = 0; i < len; i++) {
+            if(board[row][i] === val) {
+                return false
+            }
+        }
+        // 列不能重复
+        for(let i = 0; i < len; i++) {
+            if(board[i][col] === val) {
+                return false
+            }
+        }
+        let startRow = Math.floor(row / 3) * 3
+        let startCol = Math.floor(col / 3) * 3
+
+        for(let i = startRow; i < startRow + 3; i++) {
+            for(let j = startCol; j < startCol + 3; j++) {
+                if(board[i][j] === val) {
+                    return false
+                }
+            }
+        }
+
+        return true
+    }
 
+    function backTracking() {
+        for(let i = 0; i < board.length; i++) {
+            for(let j = 0; j < board[0].length; j++) {
+                if(board[i][j] !== '.') continue
+                for(let val = 1; val <= 9; val++) {
+                    if(isValid(i, j, `${val}`, board)) {
+                        board[i][j] = `${val}`
+                        if (backTracking()) {
+                            return true
+                        }
+                        
+                        board[i][j] = `.`
+                    }
+                }
+                return false
+            }
+        }
+        return true
+    }
+    backTracking(board)
+    return board
+    
+};
+```
 
 
 -----------------------

problems/0051.N皇后.md

@@ -430,6 +430,65 @@ func solveNQueens(n int) [][]string {
 }
 ```
 
+Javascript:
+```Javascript
+var solveNQueens = function(n) {
+    function isValid(row, col, chessBoard, n) {
+
+        for(let i = 0; i < row; i++) {
+            if(chessBoard[i][col] === 'Q') {
+                return false
+            }
+        }
+
+        for(let i = row - 1, j = col - 1; i >= 0 && j >= 0; i--, j--) {
+            if(chessBoard[i][j] === 'Q') {
+                return false
+            }
+        }
+
+        for(let i = row - 1, j = col + 1; i >= 0 && j < n; i--, j++) {
+            if(chessBoard[i][j] === 'Q') {
+                return false
+            }
+        }
+        return true
+    }
+
+    function transformChessBoard(chessBoard) {
+        let chessBoardBack = []
+        chessBoard.forEach(row => {
+            let rowStr = ''
+            row.forEach(value => {
+                rowStr += value
+            })
+            chessBoardBack.push(rowStr)
+        })
+
+        return chessBoardBack
+    }
+
+    let result = []
+    function backtracing(row,chessBoard) {
+        if(row === n) {
+            result.push(transformChessBoard(chessBoard))
+            return
+        }
+        for(let col = 0; col < n; col++) {
+            if(isValid(row, col, chessBoard, n)) {
+                chessBoard[row][col] = 'Q'
+                backtracing(row + 1,chessBoard)
+                chessBoard[row][col] = '.'
+            }
+        }
+    }
+    let chessBoard = new Array(n).fill([]).map(() => new Array(n).fill('.'))
+    backtracing(0,chessBoard)
+    return result
+    
+};
+```
+
 
 
 -----------------------

problems/0077.组合.md

@@ -370,23 +370,21 @@ class Solution {
 
 
 Python：
-```python
+```python3
 class Solution:
-    result: List[List[int]] = []
-    path: List[int] = []
     def combine(self, n: int, k: int) -> List[List[int]]:
-      self.result = []
-      self.combineHelper(n, k, 1)
-      return self.result
-
-    def combineHelper(self, n: int, k: int, startIndex: int):
-      if  (l := len(self.path)) == k:
-        self.result.append(self.path.copy())
-        return
-      for i in range(startIndex, n - (k - l) + 2):
-        self.path.append(i)
-        self.combineHelper(n, k, i + 1)
-        self.path.pop()
+        res=[]  #存放符合条件结果的集合
+        path=[]  #用来存放符合条件结果
+        def backtrack(n,k,startIndex):
+            if len(path) == k:
+                res.append(path[:])
+                return 
+            for i in range(startIndex,n+1):
+                path.append(i)  #处理节点 
+                backtrack(n,k,i+1)  #递归
+                path.pop()  #回溯，撤销处理的节点
+        backtrack(n,k,1)
+        return res
 ```
 javascript
 ```javascript
@@ -438,8 +436,6 @@ func backtrack(n,k,start int,track []int){
 ```
 
 
-
-
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)

problems/0077.组合优化.md

@@ -176,9 +176,49 @@ class Solution {
 ```
 
 Python：
-
-
+```python3
+class Solution:
+    def combine(self, n: int, k: int) -> List[List[int]]:
+        res=[]  #存放符合条件结果的集合
+        path=[]  #用来存放符合条件结果
+        def backtrack(n,k,startIndex):
+            if len(path) == k:
+                res.append(path[:])
+            return 
+            for i in range(startIndex,n-(k-len(path))+2):  #优化的地方
+                path.append(i)  #处理节点 
+                backtrack(n,k,i+1)  #递归
+                path.pop()  #回溯，撤销处理的节点
+    backtrack(n,k,1)
+    return res
+```
 Go：
+```Go
+var res [][]int 
+func combine(n int, k int) [][]int {
+   res=[][]int{}
+   if n <= 0 || k <= 0 || k > n {
+		return res
+	}
+    backtrack(n, k, 1, []int{})
+	return res
+}
+func backtrack(n,k,start int,track []int){
+    if len(track)==k{
+        temp:=make([]int,k)
+        copy(temp,track)
+        res=append(res,temp)
+    }
+    if len(track)+n-start+1 < k {
+			return
+		}
+    for i:=start;i<=n;i++{ 
+        track=append(track,i)
+        backtrack(n,k,i+1,track)
+        track=track[:len(track)-1]
+    }
+}
+```
 
 
 

problems/0106.从中序与后序遍历序列构造二叉树.md

@@ -580,8 +580,10 @@ tree2 的前序遍历是[1 2 3]， 后序遍历是[3 2 1]。
 
 ## 其他语言版本
 
-
 Java：
+
+106.从中序与后序遍历序列构造二叉树
+
 ```java
 class Solution {
     public TreeNode buildTree(int[] inorder, int[] postorder) {
@@ -617,8 +619,43 @@ class Solution {
 }
 ```
 
+105.从前序与中序遍历序列构造二叉树
+
+```java
+class Solution {
+    public TreeNode buildTree(int[] preorder, int[] inorder) {
+        return helper(preorder, 0, preorder.length - 1, inorder, 0, inorder.length - 1);
+    }
+
+    public TreeNode helper(int[] preorder, int preLeft, int preRight,
+                           int[] inorder, int inLeft, int inRight) {
+        // 递归终止条件
+        if (inLeft > inRight || preLeft > preRight) return null;
+
+        // val 为前序遍历第一个的值，也即是根节点的值
+        // idx 为根据根节点的值来找中序遍历的下标
+        int idx = inLeft, val = preorder[preLeft];
+        TreeNode root = new TreeNode(val);
+        for (int i = inLeft; i <= inRight; i++) {
+            if (inorder[i] == val) {
+                idx = i;
+                break;
+            }
+        }
+
+        // 根据 idx 来递归找左右子树
+        root.left = helper(preorder, preLeft + 1, preLeft + (idx - inLeft),
+                         inorder, inLeft, idx - 1);
+        root.right = helper(preorder, preLeft + (idx - inLeft) + 1, preRight,
+                         inorder, idx + 1, inRight);
+        return root;
+    }
+}
+```
+
 Python：
 105.从前序与中序遍历序列构造二叉树
+
 ```python
 # Definition for a binary tree node.
 # class TreeNode:
@@ -637,6 +674,7 @@ class Solution:
             return root
 ```
 106.从中序与后序遍历序列构造二叉树
+
 ```python
 # Definition for a binary tree node.
 # class TreeNode:

problems/0112.路径总和.md

@@ -347,6 +347,42 @@ class Solution {
 }
 ```
 
+0113.路径总和-ii
+
+```java
+class Solution {
+    public List<List<Integer>> pathSum(TreeNode root, int targetSum) {
+        List<List<Integer>> res = new ArrayList<>();
+        if (root == null) return res; // 非空判断
+        
+        List<Integer> path = new LinkedList<>();
+        preorderDFS(root, targetSum, res, path);
+        return res;
+    }
+
+    public void preorderDFS(TreeNode root, int targetSum, List<List<Integer>> res, List<Integer> path) {
+        path.add(root.val);
+        // 遇到了叶子节点
+        if (root.left == null && root.right == null) {
+            // 找到了和为 targetSum 的路径
+            if (targetSum - root.val == 0) {
+                res.add(new ArrayList<>(path));
+            }
+            return; // 如果和不为 targetSum，返回
+        }
+
+        if (root.left != null) {
+            preorderDFS(root.left, targetSum - root.val, res, path);
+            path.remove(path.size() - 1); // 回溯
+        }
+        if (root.right != null) {
+            preorderDFS(root.right, targetSum - root.val, res, path);
+            path.remove(path.size() - 1); // 回溯
+        }
+    }
+}
+```
+
 Python：
 
 0112.路径总和

problems/0344.反转字符串.md

@@ -183,6 +183,26 @@ func reverseString(s []byte)  {
 }
 ```
 
+javaScript:
+
+```js
+/**
+ * @param {character[]} s
+ * @return {void} Do not return anything, modify s in-place instead.
+ */
+var reverseString = function(s) {
+    return s.reverse();
+};
+
+var reverseString = function(s) {
+    let l = -1, r = s.length;
+    while(++l < --r) [s[l], s[r]] = [s[r], s[l]];
+    return s;
+};
+```
+
+
+