leetcode 98 - Validate Binary Search Tree

class Solution
{
public:
    bool isValidBST(TreeNode *root)
    {
        int subLeftMax = INT_MIN, subLeftMin = INT_MAX, subRightMax = INT_MIN, subRightMin = INT_MAX;

        return this->doValid(root, &subLeftMax, &subLeftMin, &subRightMax, &subRightMin);
    }

protected:
    bool doValid(TreeNode *root, int *leftMaxVal, int *leftMinVal, int *rightMaxVal, int *rightMinVal)
    {
        bool result = true;

        int subLeftMax = INT_MIN, subLeftMin = INT_MAX, subRightMax = INT_MIN, subRightMin = INT_MAX;

        if (root == NULL || (root->left == NULL && root->right == NULL))
        {
            return true;
        }

        if ((root->left != NULL && root->left->val >= root->val) ||
            (root->right != NULL && root->right->val <= root->val))
        {
            return false;
        }

        result = this->doValid(root->left, &subLeftMax, &subLeftMin, &subRightMax, &subRightMin);

        if (result == false || (root->left != NULL && subLeftMax >= root->val)
            || (root->left != NULL && subRightMax >= root->val))
        {
            return false;
        }

        *leftMaxVal = max(max(subLeftMax, subRightMax), (root->left == NULL ? INT_MIN : root->left->val));
        *leftMinVal = min(min(subLeftMin, subRightMin), (root->left == NULL ? INT_MAX : root->left->val));

        subLeftMax = subRightMax = INT_MIN;
        subLeftMin = subRightMin = INT_MAX;

        result = this->doValid(root->right, &subLeftMax, &subLeftMin, &subRightMax, &subRightMin);

        if (result == false || (root->right != NULL && subLeftMin <= root->val)
            || (root->right != NULL &&subRightMin <= root->val))
        {
            return false;
        }

        *rightMaxVal = max(max(subLeftMax, subRightMax), (root->right == NULL ? INT_MIN : root->right->val));
        *rightMinVal = min(min(subLeftMin, subRightMin), (root->right == NULL ? INT_MAX : root->right->val));

        return  true;
    }
};