732. My Calendar III

A k-booking happens when k events have some non-empty intersection (i.e., there is some time that is common to all k events.)

You are given some events [start, end), after each given event, return an integer k representing the maximum k-booking between all the previous events.

Implement the MyCalendarThree class:

• MyCalendarThree() Initializes the object.
• int book(int start, int end) Returns an integer k representing the largest integer such that there exists a k-booking in the calendar.

class MyCalendarThree {
    map<int, int> m {{-1, 0}};
    int res;
public:
    MyCalendarThree(): res(0) {}

    int book(int start, int end) {
        auto st = m.emplace(start, (--m.upper_bound(start))->second);
        auto ed = m.emplace(end, (--m.upper_bound(end))->second);
        for(auto i = st.first; i != ed.first; i++) {
            res = max(res, ++(i->second));
        }
        return res;
    }
};

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