Balanced Binary Tree

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two sub trees of every node never differ by more than 1.

 /**  
  * 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 height(TreeNode *root){  
     if(root == NULL){  
       return 0;  
     }  
     int leftHeight = height(root->left);  
     if(leftHeight == -1){  
       return -1;  
     }  
     int rightHeight = height(root->right);  
     if(rightHeight == -1){  
       return -1;  
     }  
     if(abs(leftHeight - rightHeight) > 1){  
       return -1;  
     }  
     return 1 + max(leftHeight, rightHeight);  
   }  
   bool isBalanced(TreeNode* root) {  
     if(root == NULL){  
       return true;  
     }  
     if(height(root) == -1){  
       return false;  
     }  
     return true;  
   }  
 };