Balanced Binary Tree [LeetCode]

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

Solution: 

    bool helperBalanced(int *depth, TreeNode * root){
        if(root->left == NULL && root->right == NULL){
            (*depth) = 1;
            return true;
        }
        
        int left_depth = 0;
        int right_depth = 0;
        if(root->left != NULL){
            if(helperBalanced(&left_depth, root->left) == false)
                return false;
        }
        
        if(root->right != NULL){
            if(helperBalanced(&right_depth, root->right) == false)
                return false;
        }
        
        if(abs(right_depth - left_depth) > 1)
            return false;
        
        (*depth) = max(left_depth, right_depth) + 1;
            
        return true;
    }
    
    bool isBalanced(TreeNode *root) {
        if(root == NULL)
            return true;
        int depth= 0;
        return helperBalanced(&depth, root);
    }