LeetCode "Count Complete Tree Nodes"

DFS solution is intuitive. I put my BFS solution below:

class Solution {
public:
    int countNodes(TreeNode* root) 
    {
        if (!root) return 0;
        
        //  Case 1: complete
        int hl = 0, hr = 0;
        TreeNode *pl = root;
        while(pl)
        {
            hl ++;
            pl = pl->left;
        }
        TreeNode *pr = root;
        while(pr)
        {
            hr ++;
            pr = pr->right;
        }
        if (hl == hr)
        {
            return pow(2, hl) - 1;
        }
        
        //  Case 2: incomplete
        deque<TreeNode *> q;
        q.push_back(root);
        int pcnt = 1;
        int level = 0;
        
        while(!q.empty())
        {
            auto ptop = q.front();
            q.pop_front();
            pcnt --;

            if (ptop->left)
                q.push_back(ptop->left);
            if (ptop->right)
                q.push_back(ptop->right);

            if(pcnt == 0)
            {
                pcnt = q.size();
                level ++;
                if (level == hr)
                {
                    break;
                }
            }
        }

        return pow(2, hr) - 1 + pcnt;
    }
};