LeetCode-in-Java

731. My Calendar II

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 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 ca not 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.

Solution

import java.util.TreeMap;

public class MyCalendarTwo {
    private final TreeMap<Integer, Integer> map;
    private final TreeMap<Integer, Integer> overlap;

    public MyCalendarTwo() {
        map = new TreeMap<>();
        overlap = new TreeMap<>();
    }

    public boolean book(int start, int end) {
        Integer ol = overlap.lowerKey(end);
        if (ol == null || overlap.get(ol) <= start) {
            while (true) {
                Integer lower = map.lowerKey(end);
                if (lower == null || map.get(lower) <= start) {
                    break;
                }
                overlap.put(Math.max(start, lower), Math.min(end, map.get(lower)));
                start = Math.min(start, lower);
                end = Math.max(end, map.get(lower));
                map.remove(lower);
            }
            map.put(start, end);
            return true;
        }
        return false;
    }
}

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

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