Merge branch 'youngyangyang04:master' into master

problems/0112.路径总和.md

@@ -348,8 +348,32 @@ class Solution {
 ```
 
 Python：
+```python
+// 递归法
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def hasPathSum(self, root: TreeNode, targetSum: int) -> bool:
+        def isornot(root,targetSum)->bool:
+            if (not root.left) and (not root.right) and targetSum == 0:return True // 遇到叶子节点，并且计数为0
+            if (not root.left) and (not root.right):return False //遇到叶子节点，计数不为0
+            if root.left:
+                targetSum -= root.left.val  //只有左节点
+                if isornot(root.left,targetSum):return True  //递归，处理节点
+                targetSum += root.left.val  //回溯
+            if root.right:
+                targetSum -= root.right.val //只有右节点
+                if isornot(root.right,targetSum):return True //递归，处理右节点
+                targetSum += root.right.val //回溯
+            return False
             
-
+        if root == None:return False  //别忘记处理空TreeNode
+        else:return isornot(root,targetSum-root.val)
+```
 Go：
 
 JavaScript：

problems/0718.最长重复子数组.md

@@ -160,7 +160,28 @@ Python：
 
 
 Go：
+```Go
+func findLength(A []int, B []int) int {
+	m, n := len(A), len(B)
+	res := 0
+	dp := make([][]int, m+1)
+	for i := 0; i <= m; i++ { 
+		dp[i] = make([]int, n+1)
+	}
 
+	for i := 1; i <= m; i++ {
+		for j := 1; j <= n; j++ {
+			if A[i-1] == B[j-1] {
+				dp[i][j] = dp[i-1][j-1] + 1
+			}
+			if dp[i][j] > res {
+				res = dp[i][j]
+			}
+		}
+	}
+	return res
+}
+```
 
 
 

problems/二叉树的递归遍历.md

@@ -170,7 +170,53 @@ class Solution {
 ```
 
 Python：
+```python3
+# 前序遍历-递归-LC144_二叉树的前序遍历
+class Solution:
+    def preorderTraversal(self, root: TreeNode) -> List[int]:
+        # 保存结果
+        result = []
         
+        def traversal(root: TreeNode):
+            if root == None:
+                return
+            result.append(root.val) # 前序
+            traversal(root.left)    # 左
+            traversal(root.right)   # 右
+
+        traversal(root)
+        return result
+
+# 中序遍历-递归-LC94_二叉树的中序遍历
+class Solution:
+    def inorderTraversal(self, root: TreeNode) -> List[int]:
+        result = []
+
+        def traversal(root: TreeNode):
+            if root == None:
+                return
+            traversal(root.left)    # 左
+            result.append(root.val) # 中序
+            traversal(root.right)   # 右
+
+        traversal(root)
+        return result
+
+# 后序遍历-递归-LC145_二叉树的后序遍历
+class Solution:
+    def postorderTraversal(self, root: TreeNode) -> List[int]:
+        result = []
+
+        def traversal(root: TreeNode):
+            if root == None:
+                return
+            traversal(root.left)    # 左
+            traversal(root.right)   # 右
+            result.append(root.val) # 后序
+
+        traversal(root)
+        return result
+```
 
 Go：