Leetcode no. 124

124. Binary Tree Maximum Path Sum

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.

/** * 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) {        return iterate(root)[1];    }    private int[] iterate(TreeNode root){        int[] res= {0, Integer.MIN_VALUE};        if (root== null) return res;        int[] left= iterate(root.left);        int[] right= iterate(root.right);        int Single= Math.max(left[0], right[0])+ root.val;        res[0]= Math.max(Single, 0);        int Max= Math.max(left[1], right[1]);        res[1]= Math.max(Max, left[0]+right[0]+root.val);        return res;    }}