二叉树根节点到叶子节点的所有路径和 -- 每日一题06

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param root TreeNode类 
# @return int整型
#
class Solution:
    def sumNumbers(self , root: TreeNode) -> int:
        if root is None:
            return 0
        return self.get_trace(root, 0)
    def get_trace(self, root: TreeNode, pre_sum):
        if root is None:
            return 0
        if root.left is None and root.right is None:
            return pre_sum*10 + root.val
        else:
            pre_sum = pre_sum*10 + root.val
            return self.get_trace(root.left, pre_sum)+self.get_trace(root.right, pre_sum)