[LeetCode]题解（python）：113 Path Sum II

题目来源

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https://leetcode.com/problems/path-sum-ii/

Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.

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题意分析

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Input: a binary tree, sum

Output: list of list.

Conditions: 给定一个二叉树，将所有root-leaf的路径值和等于sum的路径返回。

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题目思路

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通过一个valuelist传递。dfs递归

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AC代码（Python）

 # Definition for a binary tree node.
 # class TreeNode(object):
 #     def __init__(self, x):
 #         self.val = x
 #         self.left = None
 #         self.right = None

 class Solution(object):
     def pathSum(self, root, sum):
         """
         :type root: TreeNode
         :type sum: int
         :rtype: List[List[int]]
         """
         def dfs(root, currsum, valuelist):
             if root.left == None and root.right == None:
                 if currsum == sum: res.append(valuelist)
             if root.left:
                 dfs(root.left, currsum+root.left.val, valuelist+[root.left.val])
             if root.right:
                 dfs(root.right, currsum+root.right.val,valuelist+[root.right.val])

         res = []
         if root ==None: return res
         dfs(root, root.val, [root.val])
         return res