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.

Code

考慮：[5 [[10 15] 20] 40]，若有連續三個 [ 代表有 triple booking。

Time Complexity: $O(n)$, Space Complexity: $O(n)$

class MyCalendarTwo {
    map<int, int> mp;
public:
    MyCalendarTwo() {
        
    }
    
    bool book(int start, int end) {
        mp[start]++;
        mp[end]--;
        int booked = 0;
        for(auto it = mp.begin(); it != mp.end(); it++) {
            booked += it->second;
            if(booked == 3) {
                mp[start]--;
                mp[end]++;
                return false;
            }
        }
        return true;
    }
};
 
/**
 * Your MyCalendarTwo object will be instantiated and called as such:
 * MyCalendarTwo* obj = new MyCalendarTwo();
 * bool param_1 = obj->book(start,end);
 */

Source

• My Calendar II - LeetCode