Merge branch 'youngyangyang04:master' into master

problems/0077.组合.md

@@ -368,6 +368,34 @@ class Solution {
 }
 ```
 
+Python2:
+```python
+class Solution(object):
+    def combine(self, n, k):
+        """
+        :type n: int
+        :type k: int
+        :rtype: List[List[int]]
+        """
+        result = []
+        path = []
+        def backtracking(n, k, startidx):
+            if len(path) == k:
+                result.append(path[:])
+                return
+
+            # 剪枝， 最后k - len(path)个节点直接构造结果，无需递归
+            last_startidx = n - (k - len(path)) + 1
+            result.append(path + [idx for idx in range(last_startidx, n + 1)])
+
+            for x in range(startidx, last_startidx):
+                path.append(x)
+                backtracking(n, k, x + 1)  # 递归
+                path.pop()  # 回溯
+
+        backtracking(n, k, 1)
+        return result
+```
 
 ## Python 
 ```python

problems/0101.对称二叉树.md

@@ -185,7 +185,8 @@ public:
         queue<TreeNode*> que;
         que.push(root->left);   // 将左子树头结点加入队列
         que.push(root->right);  // 将右子树头结点加入队列
-        while (!que.empty()) {  // 接下来就要判断这这两个树是否相互翻转
+        
+        while (!que.empty()) {  // 接下来就要判断这两个树是否相互翻转
             TreeNode* leftNode = que.front(); que.pop();
             TreeNode* rightNode = que.front(); que.pop();
             if (!leftNode && !rightNode) {  // 左节点为空、右节点为空，此时说明是对称的

problems/0235.二叉搜索树的最近公共祖先.md

@@ -268,17 +268,30 @@ class Solution {
 递归法：
 ```python
 class Solution:
+    """二叉搜索树的最近公共祖先 递归法"""
+
     def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
-        if not root: return root  //中
+        if root.val > p.val and root.val > q.val:
-        if root.val >p.val and root.val > q.val:
+            return self.lowestCommonAncestor(root.left, p, q)
-            return self.lowestCommonAncestor(root.left,p,q)  //左
+        if root.val < p.val and root.val < q.val:
-        elif root.val < p.val and root.val < q.val:
+            return self.lowestCommonAncestor(root.right, p, q)
-            return self.lowestCommonAncestor(root.right,p,q)  //右
+        return root
-        else: return root
 ```
 
 迭代法：
+```python
+class Solution:
+    """二叉搜索树的最近公共祖先 迭代法"""
 
+    def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
+        while True:
+            if root.val > p.val and root.val > q.val:
+                root = root.left
+            elif root.val < p.val and root.val < q.val:
+                root = root.right
+            else:
+                return root
+```
 
 ## Go 
 

problems/0236.二叉树的最近公共祖先.md

@@ -264,16 +264,21 @@ class Solution {
 ## Python 
 
 ```python
-//递归
 class Solution:
+    """二叉树的最近公共祖先 递归法"""
+
     def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
-        if not root or root == p or root == q: return root  //找到了节点p或者q，或者遇到空节点
+        if not root or root == p or root == q:
-        left = self.lowestCommonAncestor(root.left,p,q)  //左
+            return root
-        right = self.lowestCommonAncestor(root.right,p,q)  //右
+        
-        if left and right: return root  //中: left和right不为空，root就是最近公共节点
+        left = self.lowestCommonAncestor(root.left, p, q)
-        elif left and not right: return left  //目标节点是通过left返回的
+        right = self.lowestCommonAncestor(root.right, p, q)
-        elif not left and right: return right  //目标节点是通过right返回的
+        
-        else: return None  //没找到
+        if left and right:
+            return root
+        if left:
+            return left
+        return right
 ```
 
 ## Go 

problems/0739.每日温度.md

@@ -276,6 +276,36 @@ func dailyTemperatures(num []int) []int {
 }
 ```
 
+JavaScript：
+```javascript
+/**
+ * @param {number[]} temperatures
+ * @return {number[]}
+ */
+var dailyTemperatures = function(temperatures) {
+    let n = temperatures.length;
+    let res = new Array(n).fill(0);
+    let stack = [];  // 递减栈：用于存储元素右面第一个比他大的元素下标
+    stack.push(0);
+    for (let i = 1; i < n; i++) {
+        // 栈顶元素
+        let top = stack[stack.length - 1];
+        if (temperatures[i] < temperatures[top]) {
+            stack.push(i);
+        } else if (temperatures[i] === temperatures[top]) {
+            stack.push(i);
+        } else {
+            while (stack.length && temperatures[i] > temperatures[stack[stack.length - 1]]) {
+                let top = stack.pop();
+                res[top] = i - top;
+            }
+            stack.push(i);
+        }
+    }
+    return res;
+};
+```
+
 
 
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