731. My Calendar II

Description

You are implementing a program to use as your calendar. We can add a new event if adding the event will not cause a triple booking.

A triple booking happens when three events have some non-empty intersection (i.e., some moment is common to all the three events.).

The event can be represented as a pair of integers start and end that represents a booking on the half-open interval [start, end), the range of real numbers x such that start <= x < end.

Implement the MyCalendarTwo class:

• MyCalendarTwo() Initializes the calendar object.
• boolean book(int start, int end) Returns true if the event can be added to the calendar successfully without causing a triple booking. Otherwise, return false and do not add the event to the calendar.

 

Example 1:

Input
["MyCalendarTwo", "book", "book", "book", "book", "book", "book"]
[[], [10, 20], [50, 60], [10, 40], [5, 15], [5, 10], [25, 55]]
Output
[null, true, true, true, false, true, true]

Explanation
MyCalendarTwo myCalendarTwo = new MyCalendarTwo();
myCalendarTwo.book(10, 20); // return True, The event can be booked. 
myCalendarTwo.book(50, 60); // return True, The event can be booked. 
myCalendarTwo.book(10, 40); // return True, The event can be double booked. 
myCalendarTwo.book(5, 15);  // return False, The event cannot be booked, because it would result in a triple booking.
myCalendarTwo.book(5, 10); // return True, The event can be booked, as it does not use time 10 which is already double booked.
myCalendarTwo.book(25, 55); // return True, The event can be booked, as the time in [25, 40) will be double booked with the third event, the time [40, 50) will be single booked, and the time [50, 55) will be double booked with the second event.

 

Constraints:

• 0 <= start < end <= 109
• At most 1000 calls will be made to book.

 

Solutions

Solution: Brute Force

• Time complexity: O(n²)
• Space complexity: O(n)

 

JavaScript

const MyCalendarTwo = function () {
  this.events = [];
  this.doubleEvents = [];
};

/**
 * @param {number} start
 * @param {number} end
 * @return {boolean}
 */
MyCalendarTwo.prototype.book = function (start, end) {
  for (const event of this.doubleEvents) {
    if (start < event.end && end > event.start) return false;
  }

  for (const event of this.events) {
    if (start >= event.end || end <= event.start) continue;
    const overlayStart = Math.max(event.start, start);
    const overlayEnd = Math.min(event.end, end);

    this.doubleEvents.push({ start: overlayStart, end: overlayEnd });
  }
  this.events.push({ start, end });

  return true;
};

/**
 * Your MyCalendarTwo object will be instantiated and called as such:
 * var obj = new MyCalendarTwo()
 * var param_1 = obj.book(start,end)
 */