image.png
用回溯法！！！
前序优先遍历（dfs）, 判断是否满足条件，满足就累计一个答案，然后深度遍历，别忘了最后回溯，要删掉路径中的节点
代码：
# -*- 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 root == None:
return []
self.ans = []
path = []
currentSum = 0
self.findPath(root, expectNumber, path, currentSum)
return self.ans
def findPath(self, root, expectNumber, path, currentSum):
#if root == None:
#return
currentSum += root.val
path.append(root.val)
isleaf = (root.left == None and root.right == None)
if currentSum == expectNumber and isleaf:
tmp = []
if path:
tmp = path[:]
self.ans.append(tmp)
if root.left:
self.findPath(root.left, expectNumber, path, currentSum)
if root.right :
self.findPath(root.right, expectNumber, path, currentSum)
del path[-1]
