0379. Design Phone Directory.js

// Design a Phone Directory which supports the following operations:
//
// 1. get: Provide a number which is not assigned to anyone.
// 2. check: Check if a number is available or not.
// 3. release: Recycle or release a number.
//
// Example:
//
// // Init a phone directory containing a total of 3 numbers: 0, 1, and 2.
// PhoneDirectory directory = new PhoneDirectory(3);
//
// // It can return any available phone number. Here we assume it returns 0.
// directory.get();
//
// // Assume it returns 1.
// directory.get();
//
// // The number 2 is available, so return true.
// directory.check(2);
//
// // It returns 2, the only number that is left.
// directory.get();
//
// // The number 2 is no longer available, so return false.
// directory.check(2);
//
// // Release number 2 back to the pool.
// directory.release(2);
//
// // Number 2 is available again, return true.
// directory.check(2);

class PhoneDirectory {
  /**
   * Initialize your data structure here
   @param maxNumbers - The maximum numbers that can be stored in the phone directory.
   * @param {number} maxNumbers
   */
  constructor(maxNumbers) {
    this.len = maxNumbers;
    this.set = new Set();
    while (maxNumbers--) this.set.add(maxNumbers);
  }

  /**
   * Provide a number which is not assigned to anyone.
   @return - Return an available number. Return -1 if none is available.
   * @return {number}
   */
  get() {
    if (this.set.size === 0) return -1;
    const n = this.set.values().next().value;
    this.set.delete(n);
    return n;
  };

  /**
   * Check if a number is available or not.
   * @param {number} number
   * @return {boolean}
   */
  check(number) {
    return this.set.has(number);
  };

  /**
   * Recycle or release a number.
   * @param {number} number
   * @return {void}
   */
  release(number) {
    this.set.add(number);
  };
}