729 - My Calendar I

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.

 

C++

class MyCalendar {
public:
    map<int, int> m;

    MyCalendar() {
    }

    bool book(int start, int end) {
        ++m[start];
        --m[end];
        int s = 0;
        for (auto& [k, v] : m) {
            s += v;
            if (s > 1) {
                --m[start];
                ++m[end];
                return false;
            }
        }
        return true;
    }
};

JAVA

import java.util.Map;
import java.util.TreeMap;

class MyCalendar {

    private final TreeMap<Integer, Integer> tm = new TreeMap<>();

    public MyCalendar() {
    }

    public boolean book(int start, int end) {
        Map.Entry<Integer, Integer> ent = tm.floorEntry(start);
        if (ent != null && ent.getValue() > start) {
            return false;
        }
        ent = tm.ceilingEntry(start);
        if (ent != null && ent.getKey() < end) {
            return false;
        }
        tm.put(start, end);
        return true;
    }
}