剑指offer-平衡二叉树

public class Solution {//树 my
    public boolean IsBalanced_Solution(TreeNode root) {
        return help(root)!=-1;//-1表示不是二叉平衡树
    }
    
    public int help(TreeNode root){
        if(null==root){
            return 0;
        }
        int left = help(root.left);
        if(-1==left){
            return -1;
        }
        int right = help(root.right);
        if(-1==right||Math.abs(left-right)>1){
            return -1;
        }
        return right>left?right+1:left+1;
    }
}