Update 0257.二叉树的所有路径.md

problems/0257.二叉树的所有路径.md

@@ -473,31 +473,27 @@ class Solution {
 递归法+回溯（版本一）
 ```Python
 # 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
-import copy
-from typing import List, Optional
-
 class Solution:
-    def binaryTreePaths(self, root: Optional[TreeNode]) -> List[str]:
-        if not root:
-            return []
+    def traversal(self, cur, path, result):
+        path.append(cur.val)  # 中
+        if not cur.left and not cur.right:  # 到达叶子节点
+            sPath = '->'.join(map(str, path))
+            result.append(sPath)
+            return
+        if cur.left:  # 左
+            self.traversal(cur.left, path, result)
+            path.pop()  # 回溯
+        if cur.right:  # 右
+            self.traversal(cur.right, path, result)
+            path.pop()  # 回溯
+
+    def binaryTreePaths(self, root):
         result = []
-        self.generate_paths(root, [], result)
+        path = []
+        if not root:
+            return result
+        self.traversal(root, path, result)
         return result
-    
-    def generate_paths(self, node: TreeNode, path: List[int], result: List[str]) -> None:
-        path.append(node.val)
-        if not node.left and not node.right:
-            result.append('->'.join(map(str, path)))
-        if node.left:
-            self.generate_paths(node.left, copy.copy(path), result)
-        if node.right:
-            self.generate_paths(node.right, copy.copy(path), result)
-        path.pop()
 
 
 ```