题解 | #判断是不是平衡二叉树#

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param pRoot TreeNode类 
     * @return bool布尔型
     */
    public boolean IsBalanced_Solution (TreeNode pRoot) {
        // write code here
        if(pRoot==null){
            return true;
        }
        int res = IsBalanced_Solution1(pRoot);
        return res>=0;
    }

    public int IsBalanced_Solution1 (TreeNode pRoot) {
        // write code here
        if(pRoot==null){
            return 0;
        }
        int a = IsBalanced_Solution1(pRoot.left);
        int b = IsBalanced_Solution1(pRoot.right);
        if(a>=0 && b>=0 && Math.abs(a-b)<=1){
            return Math.max(a,b)+1;
        }else{
            return -1;
        }
        
    }
}