leetcode 129. 求根到叶子节点数字之和

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题目链接：leetcode

思路：
广度优先

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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
from collections import deque
class Solution:
    def sumNumbers(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        if not root:return 0
        res = 0
        q = deque()
        q.append((root,root.val))
        while q:
            node,val = q.popleft()
            #leaf node
            if not node.left and not node.right:
                res += val
            if node.left:
                q.append((node.left,node.left.val+val*10))
            if node.right:
                q.append((node.right,node.right.val+val*10))
        return res