二叉树中的最大路径和

给出一棵二叉树，寻找一条路径使其路径和最大，路径可以在任一节点中开始和结束（路径和为两个节点之间所在路径上的节点权值之和）

样例

给出一棵二叉树：

       1      / \     2   3

返回 6

/** * Definition of TreeNode: * class TreeNode { * public: *     int val; *     TreeNode *left, *right; *     TreeNode(int val) { *         this->val = val; *         this->left = this->right = NULL; *     } * } */class Solution {public:    /**     * @param root: The root of binary tree.     * @return: An integer     */    int maxPathSum(TreeNode *root) {        // write your code here        if (root == NULL)        {            return 0;        }        int result = INT_MIN;        visit(root, result);        return result;    }private:    int visit(TreeNode *root, int &result)    {        if (root == NULL)        {            return 0;        }            int left = visit(root->left, result);        int right = visit(root->right, result);        int temp = max(left+right, max(left, right));        temp = max(root->val, temp + root->val);        if (temp > result)        {            result = temp;        }        int maxBranch = max(left, right) + root->val;        return max(maxBranch, root->val);    }};