/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int ans(TreeNode *root,bool &f){
        if(root==NULL)return 0;


        int l=ans(root->left,f);
        int r=ans(root->right,f);

        if(l-r>1||r-l>1)f=false;
        return max(l,r)+1;
    }
    bool isBalanced(TreeNode* root) {
        //但凡一个不是，就都不是
        if(root==NULL)return true;
        else {
            bool f=true;
            ans(root,f);
            return f;

        }



    }
};