L3：05 - Binary Tree Maximum Path Sum

https://oj.leetcode.com/problems/binary-tree-maximum-path-sum/

Given a binary tree, find the maximum path sum. The path may start and end at any node in the tree. For example: Given the below binary tree, 1 / \ 2 3 Return 6.

/** * Copyright: NineChapter * - Algorithm Course, Mock Interview, Interview Questions * - More details on: http://www.ninechapter.com/ */public class Solution {    private class ResultType {        int singlePath, maxPath;        ResultType(int singlePath, int maxPath) {            this.singlePath = singlePath;            this.maxPath = maxPath;        }    }    private ResultType helper(TreeNode root) {        if (root == null) {            return new ResultType(0, Integer.MIN_VALUE);        }        // Divide        ResultType left = helper(root.left);        ResultType right = helper(root.right);        // Conquer        int singlePath = Math.max(left.singlePath, right.singlePath) + root.val;        singlePath = Math.max(singlePath, 0);        int maxPath = Math.max(left.maxPath, right.maxPath);        maxPath = Math.max(maxPath, left.singlePath + right.singlePath + root.val);        return new ResultType(singlePath, maxPath);    }    public int maxPathSum(TreeNode root) {        ResultType result = helper(root);        return result.maxPath;    }}