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.

Solution:
Check sub-trees' height for each node.
Tips: recursion.

 /**
 * Definition for binary tree
 * 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 (differ(getDepth(root.left, 0),getDepth(root.right, 0)) > 1) return false;
        return (isBalanced(root.left) && isBalanced(root.right));
    }
    public int getDepth(TreeNode root, int depth){
        if (root == null) return depth;
        return Math.max(getDepth(root.left, depth + 1), getDepth(root.right, depth + 1));
    }
    public int differ(int A, int B){
        return Math.abs(A-B);
    }
}