Binary Tree Maximum Path Sum

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int maxPathSum(TreeNode *root) {
        int ret = INT_MIN;
        getSum(root, ret);
        return ret;
    }
    
private:
    int getSum(TreeNode *node, int &ret) {
        if (node == NULL) return 0;
        int l = getSum(node->left, ret);
        int r = getSum(node->right, ret);
        int cret = max(node->val, max(l, r) + node->val);
        ret = max(ret, max(cret, l + r + node->val));
        return cret;
    }
};