python剑指offer系列二叉树中和为某一值的路径

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    # 返回二维列表，内部每个列表表示找到的路径
    def FindPath(self, root, expectNumber):
        # write code here
        if not root:
            return []
        if root.val == expectNumber and not root.left and not root.right:
            return [[root.val]]
        result = []
        left = self.FindPath(root.left, expectNumber - root.val)
        right = self.FindPath(root.right, expectNumber - root.val)
        for i in left + right:
            result.append([root.val] + i)#？？？？不太懂，花点时间想想
        return result