Balanced Binary Tree @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.
 * 
 */
public class S110 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

	}
	
	public boolean isBalanced(TreeNode root) {
        if(root == null){
        	return true;
        }
        // 如果子树高度差大于1，则不平衡
        if(Math.abs(depth(root.left)-depth(root.right)) > 1){
        	return false;
        }
        // 递归检查左子树和右子树的平衡性
        return isBalanced(root.left) && isBalanced(root.right);
    }

	// 帮助方法，返回树的高度
	private int depth(TreeNode root){
		if(root == null){
			return 0;
		}
		return 1 + Math.max(depth(root.left), depth(root.right));
	}
}