LeetCode in Kotlin

729. My Calendar I

Medium

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

A double booking happens when two events have some non-empty intersection (i.e., some moment is common to both 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 MyCalendar class:

• MyCalendar() 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 double booking. Otherwise, return false and do not add the event to the calendar.

Example 1:

Input

[“MyCalendar”, “book”, “book”, “book”]

[[], [10, 20], [15, 25], [20, 30]]

Output: [null, true, false, true]

Explanation:

MyCalendar myCalendar = new MyCalendar(); 
myCalendar.book(10, 20); // return True 
myCalendar.book(15, 25); // return False, It can not be booked because time 15 is already booked by another event. 
myCalendar.book(20, 30); // return True, The event can be booked, as the first event takes every time less than 20, but not including 20.

Constraints:

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

Solution

import java.util.TreeSet

class MyCalendar {
    internal class Meeting(val start: Int, val end: Int) : Comparable<Meeting?> {
        override operator fun compareTo(other: Meeting?): Int {
            return start - other!!.start
        }
    }

    private val meetings: TreeSet<Meeting> = TreeSet()

    fun book(start: Int, end: Int): Boolean {
        val meetingToBook = Meeting(start, end)
        val prevMeeting = meetings.floor(meetingToBook)
        val nextMeeting = meetings.ceiling(meetingToBook)
        if ((prevMeeting == null || prevMeeting.end <= meetingToBook.start) &&
            (nextMeeting == null || meetingToBook.end <= nextMeeting.start)
        ) {
            meetings.add(meetingToBook)
            return true
        }
        return false
    }
}

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

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