Leetcode: 113. Path Sum II

题目

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

Note: A leaf is a node with no children.

Example:

Given the below binary tree and sum = 22,5/ \4   8/   / \11  13  4/  \    / \
7    2  5   1

Return:

[[5,4,11,2],[5,8,4,5]
]

解题思路

忘了BFS和DFS的我，这道题有点蒙圈。贴一个介绍的博客基本算法——深度优先搜索（DFS）和广度优先搜索（BFS）

队列先进先出，用于BFS；栈后进先出，用于DFS。

BFS+queue

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = Noneclass Solution:def pathSum(self, root: TreeNode, sum: int) -> List[List[int]]:if not root:return []res = []queue = [(root, root.val, [root.val])]while queue:curr, val, ls = queue.pop(0) ## 先进先出，每一层都是先左后右。if not curr.left and not curr.right and val == sum:res.append(ls)if curr.left:queue.append((curr.left, val+curr.left.val, ls+[curr.left.val]))if curr.right:queue.append((curr.right, val+curr.right.val, ls+[curr.right.val]))return res

DFS+stack

class Solution:def pathSum(self, root: TreeNode, sum: int) -> List[List[int]]:if root is None:return []res = []stack = [(root, root.val, [root.val])]while stack:curr, val, ls = stack.pop()if not curr.left and not curr.right and val == sum:res.append(ls)if curr.right:stack.append((curr.right, val+curr.right.val, ls+[curr.right.val]))if curr.left:stack.append((curr.left, val+curr.left.val, ls+[curr.left.val]))return res

Leetcode: 113. Path Sum II相关推荐

[LeetCode]113.Path Sum II
[题目] Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the giv ...
LeetCode 113. Path Sum II
113. Path Sum II Given a binary tree and a sum, find all root-to-leaf paths where each path's sum eq ...
leetcode 112. Path Sum, 113. Path Sum II | 112,113. 路径总和 I, II（Java）
题目 https://leetcode.com/problems/path-sum/ https://leetcode.com/problems/path-sum-ii/ 题解简单的遍历二叉树,不解 ...
113. Path Sum II
/** 113. Path Sum II * 11.18 By Mingyang* 典型的backtracking,不过注意,这里的值可能是负数,所以不能用sum小于0来做任何判断* 1.长度标准:无 ...
LeetCode OJ 113. Path Sum II
Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given su ...
【leetcode】Path Sum II
Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given su ...
LeetCode OJ - Path Sum II
题目: Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the give ...
Leetcode: mimimum depth of tree, path sum, path sum II
思路: 简单搜索总结: dfs 框架 1. 需要打印路径. 在 dfs 函数中假如 vector 变量, 不用 & 修饰的话就不需要 undo 2. 不需要打印路径, 可设置全局变量 ans ...
LeetCode 167.Two Sum II 解题报告
LeetCode 167.Two Sum II 解题报告题目描述 Given an array of integers that is already sorted in ascending ord ...

Leetcode: 113. Path Sum II

题目

解题思路

Leetcode: 113. Path Sum II相关推荐

最新文章

热门文章