//判断一颗二叉树是否是平衡二叉树
public class AvlTree{
	 
	 //二叉树节点的定义
	 public static class Node{

	 	public int value;

	 	public Node left;
        public Node right;

        public Node(int data)
        {

        	this.value=data;
        }
	 }
   

    //判断一颗二叉树是否为平衡二叉树(利用二叉树的后序遍历)
	 public static boolean isAVL(Node head)
	 {

	   boolean[]res=new boolean[1];
	   res[0]=true;
	   getHeight(head,1,res);
	   return res[0];
        

	 }

	 //递归调用获得子树的高度和是否为平衡二叉树
	public static int getHeight(Node head,int level,boolean[]res)
	{
		if(head==null)
		{
			return level;
		}
		//左子树高度
		int lH=getHeight(head.left,level+1,res);
		if(!res[0])
		{
			return level;
		}
		//右子树高度
		int rH=getHeight(head.right,level+1,res);
		if(!res[0])
		{
			return level;
		}
	    //左右子树高度差
		if(Math.abs(lH-rH)>1)
		{
			res[0]=false;
		}
		return Math.max(lH,rH);
	} 
	public static void main(String[] args)
	{
        /**
                 1
              2     3
           4    5  6   7
        */

        Node head = new Node(1);
		head.left = new Node(2);
		head.right = new Node(3);
		head.left.left = new Node(4);
		head.left.right = new Node(5);
		head.right.left = new Node(6);
		head.right.right = new Node(7);
        
        /** 
              1
             2
            4
        */
        Node node=new Node(1);
        node.left=new Node(2);
        node.left.left=new Node(4);
        //node.right=new Node(3);

		System.out.println(isAVL(head));
        System.out.println(isAVL(node));

	}
}