my-calendar-iii.js

/**
 * My Calendar III
 *
 * Implement a MyCalendarThree class to store your events. A new event can always be added.
 *
 * Your class will have one method, book(int start, int end). Formally, this represents a booking
 * on the half open interval [start, end), the range of real numbers x such that start <= x < end.
 *
 * A K-booking happens when K events have some non-empty intersection (ie., there is some time that
 * is common to all K events.)
 *
 * For each call to the method MyCalendar.book, return an integer K representing the largest integer
 * such that there exists a K-booking in the calendar.
 *
 * This is to find the maximum number of concurrent ongoing event at any time.
 *
 * Your class will be called like this: MyCalendarThree cal = new MyCalendarThree();
 * MyCalendarThree.book(start, end)
 *
 * Example 1:
 *
 * MyCalendarThree();
 * MyCalendarThree.book(10, 20); // returns 1
 * MyCalendarThree.book(50, 60); // returns 1
 * MyCalendarThree.book(10, 40); // returns 2
 * MyCalendarThree.book(5, 15);  // returns 3
 * MyCalendarThree.book(5, 10);  // returns 3
 * MyCalendarThree.book(25, 55); // returns 3
 *
 * Explanation:
 *
 * The first two events can be booked and are disjoint, so the maximum K-booking is a 1-booking.
 * The third event [10, 40) intersects the first event, and the maximum K-booking is a 2-booking.
 * The remaining events cause the maximum K-booking to be only a 3-booking.
 * Note that the last event locally causes a 2-booking, but the answer is still 3 because
 * eg. [10, 20), [10, 40), and [5, 15) are still triple booked.
 */

/**
 * Your MyCalendarThree object will be instantiated and called as such:
 * var obj = Object.create(MyCalendarThree).createNew()
 * var param_1 = obj.book(start,end)
 */

class MyCalendarThree {
  constructor() {
    this.timeline = {};
  }

  /**
   * @param {number} start
   * @param {number} end
   * @return {number}
   */
  book(start, end) {
    // 1 new event will be starting at [s]
    this.timeline[start] = ~~this.timeline[start] + 1;
    // 1 new event will be ending at [e];
    this.timeline[end] = ~~this.timeline[end] - 1;

    let ongoing = 0;
    let k = 0;

    // Here we make sure we go though the keys in order of key value
    for (let v of Object.values(this.timeline)) {
      k = Math.max(k, (ongoing += v));
    }

    return k;
  }
}

export { MyCalendarThree };