# My Calendar II Problem

## Description

LeetCode Problem 731.

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:

``````1
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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 <= 10^9
• At most 1000 calls will be made to book.

## Sample C++ Code

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class MyCalendarTwo {
// key: time; val: +1 if start, -1 if end
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);
*/
``````