balanced-binary-tree leetcode C++

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.

C++

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isBalanced(TreeNode *root) {
        if(NULL == root) 
            return true;
        if(abs(getDeep(root->left) - getDeep(root->right)) > 1)
            return false;
        return isBalanced(root->left) && isBalanced(root->right);
    }
    int getDeep(TreeNode *root){
        if(NULL == root) 
            return 0;
        return max(getDeep(root->left),getDeep(root->right)) + 1;
    }
};