Leetcode Binary Tree Maximum Path Sum

class Solution {
public:
    int maxSum = INT_MIN;
    int getMaxSum(TreeNode* root){
        if(root == NULL) return 0;
        int leftSum = getMaxSum(root->left), rightSum = getMaxSum(root->right);
        int curSum =  max(root->val, max(root->val+leftSum, root->val+rightSum));
        maxSum = max(maxSum,max(curSum,root->val+leftSum+rightSum));
        return curSum;
    }

    int maxPathSum(TreeNode *root){
        getMaxSum(root);
        return maxSum;
    }
};