Design a phone directory that initially has maxNumbers empty slots that can store numbers. The directory should store numbers, check if a certain slot is empty or not, and empty a given slot. Implement the PhoneDirectory class: PhoneDirectory(int maxNumbers) Initializes the phone directory with the number of available slots maxNumbers. int get() Provides a number that is not assigned to anyone. Returns -1 if no number is available. bool check(int number) Returns true if the slot number is available and false otherwise. void release(int number) Recycles or releases the slot number. Example 1: Input ["PhoneDirectory", "get", "get", "check", "get", "check", "release", "check"] [[3], [], [], [2], [], [2], [2], [2]] Output [null, 0, 1, true, 2, false, null, true] Explanation PhoneDirectory phoneDirectory = new PhoneDirectory(3); phoneDirectory.get(); // It can return any available phone number. Here we assume it returns 0. phoneDirectory.get(); // Assume it returns 1. phoneDirectory.check(2); // The number 2 is available, so return true. phoneDirectory.get(); // It returns 2, the only number that is left. phoneDirectory.check(2); // The number 2 is no longer available, so return false. phoneDirectory.release(2); // Release number 2 back to the pool. phoneDirectory.check(2); // Number 2 is available again, return true. Constraints: 1 <= maxNumbers <= 104 0 <= number < maxNumbers At most 2 * 104 calls will be made to get, check, and release.