AVL tree .isPerfect()

Data Structures
1

I can’t find the solution in anywhere on the AVLtree.java in /src folder. Can anyone show me the complete answer for that?
My best guess now is to compare the number of leaf node of the tree to the max number of leaf it should have at n height. It works for me. I just don’t know if there is edge cases I’ve missed.

public boolean isPerfect(){
        return countLeaf(root)== Math.pow(2,height(root));
    }



    private int countLeaf(AVLNode root){
        if(root==null) return 0;
        if(root.left==null&&root.right==null) return 1 ;
        return countLeaf(root.left) + countLeaf(root.right);
    }