Balanced Binary Tree

/*

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 subtrees of every node never differ by more than 1.

*/
/**
 * 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 abs(int value){
      if(value<0) return (-1)*value;
      return value;
    }
    int height(TreeNode *node, bool & isBalance){
       if(node==NULL) return 0;
       if(((abs(height(node->left,isBalance)-height(node->right, isBalance)))>1) && isBalance==true){
          isBalance = false;
       }
       if (isBalance) return max(height(node->left, isBalance), height(node->right, isBalance))+1; 
       else return 0;
    }
    bool isBalanced(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        bool isBalance = true;
        height(root, isBalance);
        return isBalance;
    }
};