0124. Binary Tree Maximum Path Sum (H)
2021/8/27 6:09:03
本文主要是介绍0124. Binary Tree Maximum Path Sum (H),对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
Binary Tree Maximum Path Sum (H)
题目
A path in a binary tree is a sequence of nodes where each pair of adjacent nodes in the sequence has an edge connecting them. A node can only appear in the sequence at most once. Note that the path does not need to pass through the root.
The path sum of a path is the sum of the node's values in the path.
Given the root
of a binary tree, return the maximum path sum of any path.
Example 1:
Input: root = [1,2,3] Output: 6 Explanation: The optimal path is 2 -> 1 -> 3 with a path sum of 2 + 1 + 3 = 6.
Example 2:
Input: root = [-10,9,20,null,null,15,7] Output: 42 Explanation: The optimal path is 15 -> 20 -> 7 with a path sum of 15 + 20 + 7 = 42.
Constraints:
- The number of nodes in the tree is in the range
[1, 3 * 10^4]
. -1000 <= Node.val <= 1000
题意
给定一个二叉树,在树中找到任意一条路径(起点随意,终点随意),使得这条路径上结点值的和最大。
思路
递归处理。对于一个以 root 为根结点的子树,我们计算以 root.left 为起点并向下延伸的路径的最大和 a,以及以 root.right 为起点并向下延伸的路径的最大和 b,将 a, b, root.val 相加就得到了经过 root 的路径的最大和。对每一个结点都做相同的处理,就得到了全局最大路径和。由此可以定义我们的递归函数 int dfs(TreeNode root)
,其返回值是以 root 为起点并向下延伸的路径的最大和,dfs(root.left) + dfs(root.right) + root.val
为经过 root 的最大路径和。注意负数值的处理。
代码实现
Java
class Solution { private int maxSum; public int maxPathSum(TreeNode root) { maxSum = Integer.MIN_VALUE; dfs(root); return maxSum; } private int dfs(TreeNode root) { if (root == null) { return 0; } int leftPathSum = Math.max(dfs(root.left), 0); int rightPathSum = Math.max(dfs(root.right), 0); maxSum = Math.max(maxSum, leftPathSum + rightPathSum + root.val); return Math.max(leftPathSum, rightPathSum) + root.val; } }
这篇关于0124. Binary Tree Maximum Path Sum (H)的文章就介绍到这儿,希望我们推荐的文章对大家有所帮助,也希望大家多多支持为之网!
- 2024-09-28AI给的和自己写的Python代码,都无法改变输入框的内容,替换也不行
- 2024-09-27Sentinel配置限流资料:新手入门教程
- 2024-09-27Sentinel配置限流资料详解
- 2024-09-27Sentinel限流资料:新手入门教程
- 2024-09-26Sentinel限流资料入门详解
- 2024-09-26Springboot框架资料:初学者入门教程
- 2024-09-26Springboot框架资料详解:新手入门教程
- 2024-09-26Springboot企业级开发资料:新手入门指南
- 2024-09-26SpringBoot企业级开发资料新手指南
- 2024-09-26Springboot微服务资料入门教程