[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