Count Complete Tree Nodes

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int countNodes(TreeNode root) {
        if(root==null) return 0;
        int rh = rightH(root);
        int lh = leftH(root);
        if(rh==lh){
            return (int) Math.pow(2,rh)-1;
        }else
            return countNodes(root.left) + countNodes(root.right)+1;
    }
    int rightH(TreeNode root){
        int cnt=1;
        while(root.right!=null){
            cnt++;
            root = root.right;
        }        
        return cnt;
    }
    int leftH(TreeNode root){
        int cnt=1;
        while(root.left!=null){
            cnt++;
            root = root.left;
        }        
        return cnt;
    }
}