The description of the problem

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.

 source ： Power button （LeetCode）
 link ：https://leetcode.cn/problems/my-calendar-ii

an example

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.

 source ： Power button （LeetCode）
 link ：https://leetcode.cn/problems/my-calendar-ii
 Copyright belongs to the network . For commercial reprint, please contact the official authority , Non-commercial reprint please indicate the source .

The codes 1

class MyCalendarTwo {
    
private:
    vector<pair<int, int>> books;
    vector<pair<int, int>> overlaps;
public:
    MyCalendarTwo() {
    

    }
    
    bool book(int start, int end) {
    
        for (auto &[l, r] : overlaps) {
    
            if (start < r && l <end) {
    
                return false;
            }
        }
        for (auto &[l, r] : books) {
    
            if (start < r && l <end) {
    
                overlaps.emplace_back(make_pair(max(l, start), min(r, end)));
            }
        }
        books.emplace_back(make_pair(start, end));
        return true;
    }
};

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

The codes 2

class MyCalendarTwo {
    
private:
    vector<pair<int, int>> books;
    vector<pair<int, int>> overlaps;
public:
    MyCalendarTwo() {
    

    }
    
    bool book(int start, int end) {
    
        for (auto &[l, r] : overlaps) {
    
            if (start < r && l <end) {
    
                return false;
            }
        }
        for (auto &[l, r] : books) {
    
            if (start < r && l <end) {
    
                overlaps.push_back(make_pair(max(l, start), min(r, end)));
            }
        }
        books.push_back(make_pair(start, end));
        return true;
    }
};

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

The codes 3

class MyCalendarTwo {
    
private:
    vector<pair<int, int>> books;
    vector<pair<int, int>> overlaps;
public:
    MyCalendarTwo() {
    

    }
    
    bool book(int start, int end) {
    
        for (auto &[l, r] : overlaps) {
    
            if (start < r && l <end) {
    
                return false;
            }
        }
        for (auto &[l, r] : books) {
    
            if (start < r && l <end) {
    
                overlaps.emplace_back(max(l, start), min(r, end));
            }
        }
        books.emplace_back(start, end);
        return true;
    }
};

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