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) {
        return getHeight(pRoot) != -1;
    }

    public int getHeight(TreeNode pRoot){
        // 1. 递归函数的结束条件
        if(pRoot == null){
            return 0;
        }

        int leftHeight = getHeight(pRoot.left);
        if(leftHeight == -1){
            return -1;
        }

        int rightHeight = getHeight((pRoot.right));
        if(rightHeight == -1){
            return -1;
        }

        if(Math.abs(leftHeight - rightHeight) > 1){
            return -1;
        }

        return Math.max(leftHeight, rightHeight) + 1;
    }
}