1.题目

题目链接

2.思想

递归求解即可，需要注意递归边界的设置。

3.代码

# 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 sumNumbers(self, root: TreeNode) -> int:        
        res = []
        num = []
        self.dfs(root,num,res)
        # print(res)
        out = list(map(int,res))
        return sum(out)
    def dfs(self,root,num,res):
        num.append(str(root.val)) # 
        if root.left is None and root.right is None: # 说明是叶子节点
            # print(num)
            res.append("".join(num))
            num.pop()
            return 
        if root.left:
            self.dfs(root.left,num,res)
        if root.right:
            self.dfs(root.right,num,res)
        num.pop()