/**

 * Definition for binary tree

 * struct TreeNode {

 *     int val;

 *     TreeNode *left;

 *     TreeNode *right;

 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

 * };

 */

class Solution {

public:

    int flag=true;

    int dfs(TreeNode *root)

    {

         if(root==NULL) return true;

         int h1,h2;

         if(root->left==NULL) h1=0;

         else h1=dfs(root->left);

         if(root->right==NULL) h2=0;

         else h2=dfs(root->right);

         if(abs(h1-h2)>1) flag=0;

         return max(h1,h2)+1;

    }

    bool isBalanced(TreeNode *root) {

        dfs(root);

        return flag;

    }

};