每日一道Leetcode - 257. 二叉树的所有路径 [DFS]

# 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 binaryTreePaths(self, root: TreeNode) -> List[str]:
        def backtrack(root,path):
            if root is None:
                return
            path += str(root.val)

            if root.left is None and root.right is None:
                res.append(path)
            else:
                path += '->'
                backtrack(root.left,path)
                backtrack(root.right,path)

        res = []
        backtrack(root,'')
        return res