Leetcode: Balanced Binary Tree

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.

 1 public class Solution {
 2     public boolean isBalanced(TreeNode root) {
 3         if (root == null) return true;
 4         if (checkBalance(root) != -1) return true;
 5         else return false;
 6     }
 7     
 8     public int checkBalance(TreeNode root) {
 9         if (root == null) return 0;
10         int leftHeight = checkBalance(root.left);
11         int rightHeight = checkBalance(root.right);
12         if (leftHeight == -1 || rightHeight == -1) return -1;
13         else if (Math.abs(leftHeight - rightHeight) > 1) return -1;
14         return Math.max(leftHeight, rightHeight) + 1;
15     }
16 }