balancedtree.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int check(TreeNode* root){
        
        if(root==NULL)   return 0;
        
        int leftheight = check(root->left);
        if(leftheight == -1)   return -1;
        
        int rightheight = check(root->right);
        if(rightheight == -1)  return -1;
        
        if(abs(leftheight - rightheight) > 1)   return -1;
        
        return max(leftheight , rightheight) + 1;
        
    }
    
    bool isBalanced(TreeNode* root) {
        
        if(root==NULL){
            return true;
        }
        
          if(check(root) == -1)  return false;
          else
          return true;
        
    }
};