Leetcode Balanced Binary Tree

class Solution {
public:
    int depth(TreeNode *root){
        if(!root) return 0;
        return 1+max(depth(root->left),depth(root->right));
    }

    bool isBalanced(TreeNode *root) {
        if(!root) return true;
        return abs(depth(root->left)-depth(root->right))<=1 && isBalanced(root->left) && isBalanced(root->right);
    }
};