《剑指Offer》刷题笔记——面试题34. 二叉树中和为某一值的路径

难度：中等

一、题目描述：

二、解题分析：

1、非递归

class Solution:
    def pathSum(self, root: TreeNode, sum_: int) -> List[List[int]]:
        if not root: return []
        stack = [([root.val], root)]
        res = []
        while stack:
            tmp, node = stack.pop()
            if not node.right and not node.left and sum(tmp) == sum_:
                res.append(tmp)
            if node.right:
                stack.append((tmp + [node.right.val], node.right))
            if node.left:
                stack.append((tmp + [node.left.val], node.left))
        return res

2、非递归

class Solution:
    def pathSum(self, root: TreeNode, sum_: int) -> List[List[int]]:
        def helper(root, tmp, sum_):
            if not root:
                return 
            if not root.left and not root.right and sum_ - root.val == 0:
                tmp += [root.val]
                res.append(tmp)
            helper(root.left, tmp + [root.val], sum_ - root.val)
            helper(root.right, tmp + [root.val], sum_ - root.val)
        res = []
        helper(root, [], sum_)
        return res