week 3 110. Balanced Binary Tree

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean isBalanced(TreeNode root) {
		if (root == null)
			return true;
 
		if (getHeight(root) == -1)
			return false;
 
		return true;
	}
  public int getHeight(TreeNode root) {
		if (root == null)
			return 0;
 
		int left = getHeight(root.left);
		int right = getHeight(root.right);
 
		if (left == -1 || right == -1)
			return -1;
 
		if (Math.abs(left - right) > 1) {
			return -1;
		}
 
		return Math.max(left, right) + 1;
 
	}
}