题目描述

# -*- 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 []
        result=[]
        def FindPathMain(root, path,currentSum):
            currentSum+=root.val
            path.append(root)
            isLeaf=root.left==None and root.right==None
            if expectNumber==currentSum and isLeaf:
                onePath=[]
                for node in path:
                    onePath.append(node.val)
                result.append(onePath)
            if expectNumber>currentSum:
                if root.left:
                    FindPathMain(root.left,path, currentSum)
                if root.right:
                    FindPathMain(root.right, path, currentSum)
            path.pop()
        FindPathMain(root,[],0)
        return result

挺复杂的，看了好一阵才想明白。写的时候能犯的错误都犯了。之后复习。

ps:A==None 和not A 之间的联系与区别？？