LeetCode:Binary Tree Maximum Path Sum

Binary Tree Maximum Path Sum

Total Accepted: 66664 Total Submissions: 282541 Difficulty: Hard

Given a binary tree, find the maximum path sum.

For this problem, a path is defined as any sequence of nodes from some starting node to any node in the tree along 

the parent-child connections. The path does not need to go through the root.

For example:
Given the below binary tree,

       1      / \     2   3

Return 6.

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 Tree Depth-first Search

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 (E) Path Sum (M) Sum Root to Leaf Numbers

思路：

DFS

java code:

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public int maxPathSum(TreeNode root) {        int[] max = new int[2];        max[1] = Integer.MIN_VALUE;        DFS(root, max);        return max[1];    }        // 自定义函数    public int DFS(TreeNode root, int[] max) {        if(root == null) return 0;        int left = Math.max(0, DFS(root.left, max));        int right = Math.max(0, DFS(root.right, max));            max[1] = Math.max(max[1], left + root.val + right);        max[0] = Math.max(left, right) + root.val;        return max[0];    }}