[LeetCode] Count Complete Tree Nodes

Problem:

Given a complete binary tree, count the number of nodes.

Java Code:

/**
 * 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 leftHeight = countLeftHeight(root);
        int rightHeight = countRightHeight(root);
        if (leftHeight == rightHeight) {
            return (int)Math.pow(2, leftHeight + 1) - 1;//Attn: Mistake ^ operator as power here.
        } 
        
        return 1 + countNodes(root.left) + countNodes(root.right);
        
    }
    
    private int countLeftHeight(TreeNode root) {
        if (root == null) {
            return -1;
        }
        return 1 + countLeftHeight(root.left);
    }
    
    private int countRightHeight(TreeNode root) {
        if (root == null) {
            return -1;
        }
        return 1 + countRightHeight(root.right);
    }
}