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.

#include<iostream>#include<vector>using namespace std;struct TreeNode {int val;TreeNode *left;TreeNode *right;TreeNode(int x) : val(x), left(NULL), right(NULL) {}};int mymax = INT_MIN;int maxSum(TreeNode *root) {if (root==NULL)return 0;int leftmax = maxSum(root->left);int rightmax = maxSum(root->right);int Value = 0;if (leftmax>0)Value+=leftmax;if (rightmax>0)Value+=rightmax;mymax = Value>mymax?Value:mymax;return max(root->val,max(leftmax+root->val,rightmax+root->val));}int maxPathSum(TreeNode *root){if (root==NULL)return 0;maxSum(root);return mymax;}