[leetcode]124. Binary Tree Maximum Path Sum

题目链接：https://leetcode.com/problems/binary-tree-maximum-path-sum/#/description

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 must contain at least one node and does not need to go through the root.

For example:
Given the below binary tree,

       1      / \     2   3

Return 6.

class Solution {public:    int maxPathSum(TreeNode* root) {        int maxPath=INT32_MIN;        dfsMaxPath(root,maxPath);        return maxPath;    }    int dfsMaxPath(TreeNode* root,int &maxPath)    {        if(!root) return 0;        int l=max(0,dfsMaxPath(root->left,maxPath));        int r=max(0,dfsMaxPath(root->right,maxPath));        maxPath=max(maxPath,l+r+root->val);        return root->val+max(l,r);    }};