Balanced Binary Tree

/**
 * 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 {
private:
    int indicator = 1;
public:
    int maxDepth(TreeNode* root) {

        if(root == NULL)
            return 0;

        int leftDepth = maxDepth(root->left);
        int rightDepth = maxDepth(root->right);
        if(leftDepth > rightDepth )
            return leftDepth + 1;
        else
            return rightDepth + 1;
    }
    void check(TreeNode *root) {

        if(root == NULL)
            return;

         if(indicator == 0)
            return;

        int heightDiffer = maxDepth(root->left) - maxDepth(root->right);
        if(heightDiffer >1 || heightDiffer < -1) {
            indicator = 0;
            return;
        }
        check(root->left);
        check(root->right);
    }
    bool isBalanced(TreeNode* root) {
        check(root);
        if(indicator == 0)
            return false;
        else 
            return true;
    }
};