g0701_0800.s0729_my_calendar_i.MyCalendar Maven / Gradle / Ivy

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package g0701_0800.s0729_my_calendar_i;

// #Medium #Binary_Search #Design #Ordered_Set #Segment_Tree #Programming_Skills_II_Day_20
// #2022_03_25_Time_17_ms_(97.23%)_Space_43_MB_(87.36%)

import java.util.TreeSet;

/**
 * 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`.
**/
@SuppressWarnings("java:S1210")
public class MyCalendar {
    static class Meeting implements Comparable {
        public final int start;
        public final int end;

        public Meeting(int start, int end) {
            this.start = start;
            this.end = end;
        }

        @Override
        public int compareTo(Meeting anotherMeeting) {
            return this.start - anotherMeeting.start;
        }
    }

    private final TreeSet meetings;

    public MyCalendar() {
        meetings = new TreeSet<>();
    }

    public boolean book(int start, int end) {
        Meeting meetingToBook = new Meeting(start, end);
        Meeting prevMeeting = meetings.floor(meetingToBook);
        Meeting 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:
 * MyCalendar obj = new MyCalendar();
 * boolean param_1 = obj.book(start,end);
 */