257. 二叉树的所有路径

给定一个二叉树，返回所有从根节点到叶子节点的路径。

说明: 叶子节点是指没有子节点的节点。

示例:

输入:

1
/
2 3

5

输出: ["1->2->5", "1->3"]

解释: 所有根节点到叶子节点的路径为: 1->2->5, 1->3

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/binary-tree-paths

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def binaryTreePaths(self, root: TreeNode) -> List[str]:
        if not root:
            return []
        children=[root.left,root.right]
        if not any(children):
            return ['1']
        
        def dfs(root,path):
            if root:
                path+=str(root.val)
                if not root.left and not root.right:
                    res.append(path)
                else:
                    path+='->'
                    dfs(root.left,path)
                    dfs(root.right,path)

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

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# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def binaryTreePaths(self, root: TreeNode) -> List[str]:   
        def dfs(root,path):
            if root:
                path+=str(root.val)
                if not root.left and not root.right:
                    res.append(path)
                else:
                    path+='->'
                    dfs(root.left,path)
                    dfs(root.right,path)

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