Merge branch 'master' of https://github.com/youngyangyang04/leetcode

Author: youngyangyang04

problems/0037.解数独.md

@@ -321,6 +321,59 @@ class Solution:
         backtrack(board)
 ```
 
+Python3:
+
+```python3
+class Solution:
+    def __init__(self) -> None:
+        self.board = []
+
+    def isValid(self, row: int, col: int, target: int) -> bool:
+        for idx in range(len(self.board)):
+            # 同列是否重复
+            if self.board[idx][col] == str(target):
+                return False
+            # 同行是否重复
+            if self.board[row][idx] == str(target):
+                return False
+            # 9宫格里是否重复
+            box_row, box_col = (row // 3) * 3 + idx // 3, (col // 3) * 3 + idx % 3
+            if self.board[box_row][box_col] == str(target):
+                return False
+        return True
+    
+    def getPlace(self) -> List[int]:
+        for row in range(len(self.board)):
+            for col in range(len(self.board)):
+                if self.board[row][col] == ".":
+                    return [row, col]
+        return [-1, -1]
+    
+    def isSolved(self) -> bool:
+        row, col = self.getPlace() # 找个空位置
+        
+        if row == -1 and col == -1: # 没有空位置，棋盘被填满的
+            return True
+        
+        for i in range(1, 10):
+            if self.isValid(row, col, i): # 检查这个空位置放i，是否合适
+                self.board[row][col] = str(i) # 放i
+                if self.isSolved(): # 合适，立刻返回, 填下一个空位置。
+                    return True
+                self.board[row][col] = "." # 不合适，回溯
+        
+        return False # 空位置没法解决
+
+    def solveSudoku(self, board: List[List[str]]) -> None:
+        """
+        Do not return anything, modify board in-place instead.
+        """
+        if board is None or len(board) == 0:
+            return
+        self.board = board
+        self.isSolved()
+```
+
 Go：
 
 Javascript:

problems/0093.复原IP地址.md

@@ -338,6 +338,46 @@ class Solution(object):
         return ans```
 ```
 
+```python3
+class Solution:
+    def __init__(self) -> None:
+        self.s = ""
+        self.res = []
+
+    def isVaild(self, s: str) -> bool:
+        if len(s) > 1 and s[0] == "0":
+            return False
+
+        if 0 <= int(s) <= 255:
+            return True
+
+        return False
+
+    def backTrack(self, path: List[str], start: int) -> None:
+        if start == len(self.s) and len(path) == 4:
+            self.res.append(".".join(path))
+            return
+
+        for end in range(start + 1, len(self.s) + 1):
+            # 剪枝
+            # 保证切割完，s没有剩余的字符。
+            if len(self.s) - end > 3 * (4 - len(path) - 1):
+                continue
+            if self.isVaild(self.s[start:end]):
+                # 在参数处，更新状态，实则创建一个新的变量
+                # 不会影响当前的状态，当前的path变量没有改变
+                # 因此递归完不用path.pop()
+                self.backTrack(path + [self.s[start:end]], end)
+
+    def restoreIpAddresses(self, s: str) -> List[str]:
+        # prune
+        if len(s) > 3 * 4:
+            return []
+        self.s = s
+        self.backTrack([], 0)
+        return self.res
+```
+
 JavaScript： 
 
 ```js

problems/0106.从中序与后序遍历序列构造二叉树.md

@@ -775,6 +775,20 @@ var buildTree = function(inorder, postorder) {
 };
 ```
 
+从前序与中序遍历序列构造二叉树
+
+```javascript
+var buildTree = function(preorder, inorder) {
+    if(!preorder.length)
+        return null;
+    let root = new TreeNode(preorder[0]);
+    let mid = inorder.findIndex((number) => number === root.val);
+    root.left = buildTree(preorder.slice(1, mid + 1), inorder.slice(0, mid));
+    root.right = buildTree(preorder.slice(mid + 1, preorder.length), inorder.slice(mid + 1, inorder.length));
+    return root;
+};
+```
+
 -----------------------
 * 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/0134.加油站.md

@@ -240,6 +240,25 @@ class Solution:
 ```
 
 Go：
+```go
+func canCompleteCircuit(gas []int, cost []int) int {
+	curSum := 0
+	totalSum := 0
+	start := 0
+	for i := 0; i < len(gas); i++ {
+		curSum += gas[i] - cost[i]
+		totalSum += gas[i] - cost[i]
+		if curSum < 0 {
+			start = i+1
+			curSum = 0
+		}
+	}
+	if totalSum < 0 {
+		return -1
+	}
+	return start
+}
+```
 
 Javascript:
 ```Javascript

problems/0151.翻转字符串里的单词.md

@@ -301,6 +301,57 @@ class Solution {
 ```
 
 
+```Python3
+class Solution:
+  #1.去除多余的空格
+        def trim_spaces(self,s):     
+            n=len(s)
+            left=0
+            right=n-1
+        
+            while left<=right and s[left]==' ':       #去除开头的空格
+                left+=1
+            while left<=right and s[right]==' ':        #去除结尾的空格
+                right=right-1
+            tmp=[]
+            while left<=right:                                    #去除单词中间多余的空格
+                if s[left]!=' ':
+                    tmp.append(s[left])
+                elif tmp[-1]!=' ':                                  #当前位置是空格，但是相邻的上一个位置不是空格，则该空格是合理的
+                    tmp.append(s[left])
+                left+=1
+            return tmp
+#2.翻转字符数组
+        def reverse_string(self,nums,left,right):
+            while left<right:
+                nums[left], nums[right]=nums[right],nums[left]
+                left+=1
+                right-=1
+            return None
+#3.翻转每个单词
+        def reverse_each_word(self, nums):
+            start=0
+            end=0
+            n=len(nums)
+            while start<n:
+                while end<n and nums[end]!=' ':
+                    end+=1
+                self.reverse_string(nums,start,end-1)
+                start=end+1
+                end+=1
+            return None
+
+#4.翻转字符串里的单词
+        def reverseWords(self, s): #测试用例："the sky is blue"
+            l = self.trim_spaces(s)                     #输出：['t', 'h', 'e', ' ', 's', 'k', 'y', ' ', 'i', 's', ' ', 'b', 'l', 'u', 'e'
+            self.reverse_string( l,  0, len(l) - 1)   #输出：['e', 'u', 'l', 'b', ' ', 's', 'i', ' ', 'y', 'k', 's', ' ', 'e', 'h', 't']
+            self.reverse_each_word(l)               #输出：['b', 'l', 'u', 'e', ' ', 'i', 's', ' ', 's', 'k', 'y', ' ', 't', 'h', 'e']
+            return ''.join(l)                                 #输出：blue is sky the
+
+
+'''
+
+
 Go：
 
 ```go

problems/0209.长度最小的子数组.md

@@ -109,7 +109,7 @@ public:
 };
 ```
 
-时间复杂度：$O(n)$
+时间复杂度：$O(n)$   
 空间复杂度：$O(1)$
 
 **一些录友会疑惑为什么时间复杂度是O(n)**。
@@ -118,8 +118,8 @@ public:
 
 ## 相关题目推荐
 
-* 904.水果成篮
-* 76.最小覆盖子串
+* [904.水果成篮](https://leetcode-cn.com/problems/fruit-into-baskets/)
+* [76.最小覆盖子串](https://leetcode-cn.com/problems/minimum-window-substring/)
 
 
 

problems/0235.二叉搜索树的最近公共祖先.md

@@ -265,6 +265,54 @@ class Solution:
         else: return root
 ```
 Go：
+> BSL法
+
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val   int
+ *     Left  *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+//利用BSL的性质（前序遍历有序）
+func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
+    if root==nil{return nil}
+    if root.Val>p.Val&&root.Val>q.Val{//当前节点的值大于给定的值，则说明满足条件的在左边
+        return lowestCommonAncestor(root.Left,p,q)
+    }else if root.Val<p.Val&&root.Val<q.Val{//当前节点的值小于各点的值，则说明满足条件的在右边
+        return lowestCommonAncestor(root.Right,p,q)
+    }else {return root}//当前节点的值在给定值的中间（或者等于），即为最深的祖先
+}
+```
+
+> 普通法
+
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val   int
+ *     Left  *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+//递归会将值层层返回
+func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
+    //终止条件
+    if root==nil||root.Val==p.Val||root.Val==q.Val{return root}//最后为空或者找到一个值时，就返回这个值
+    //后序遍历
+    findLeft:=lowestCommonAncestor(root.Left,p,q)
+    findRight:=lowestCommonAncestor(root.Right,p,q)
+    //处理单层逻辑
+    if findLeft!=nil&&findRight!=nil{return root}//说明在root节点的两边
+    if findLeft==nil{//左边没找到，就说明在右边找到了
+        return findRight
+    }else {return findLeft}
+}
+```
+
 
 
 

problems/0435.无重叠区间.md

@@ -228,7 +228,27 @@ class Solution:
 
 Go：
 
-
+Javascript:
+```Javascript
+var eraseOverlapIntervals = function(intervals) {
+    intervals.sort((a, b) => {
+        return a[1] - b[1]
+    })
+
+    let count = 1
+    let end = intervals[0][1]
+
+    for(let i = 1; i < intervals.length; i++) {
+        let interval = intervals[i]
+        if(interval[0] >= right) {
+            end = interval[1]
+            count += 1
+        }
+    }
+    
+    return intervals.length - count
+};
+```
 
 
 -----------------------