Maximum path sum from any node

Given a binary tree, the task is to find the maximum path sum. The path may start and end at any node in the tree.

• Time : O(n)
• Space : O(1)

class Solution {
    int res = INT_MIN;
    int helper(Node* node) {
        if(!node) return 0;
        int l = helper(node->left);
        int r = helper(node->right);
        res = max(res, l + r + node->data);
        int ma = max(max(l,r) + node->data, node->data);
        res = max(res, ma);
        return ma;
    }
  public:
    //Function to return maximum path sum from any node in a tree.
    int findMaxSum(Node* root)
    {
        helper(root);
        return res;
    }
};