[LeetCode] My Calendar III 我的日歷之三

 

Implement a MyCalendarThree class to store your events. A new event can always be added.

Your class will have one method, book(int start, int end). Formally, this represents a booking on the half open interval [start, end), the range of real numbers x such that start <= x < end.

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

For each call to the method MyCalendar.book, return an integer K representing the largest integer such that there exists a K-booking in the calendar.

Your class will be called like this:  MyCalendarThree cal = new MyCalendarThree();  MyCalendarThree.book(start, end)

Example 1:

MyCalendarThree();
MyCalendarThree.book(10, 20); // returns 1
MyCalendarThree.book(50, 60); // returns 1
MyCalendarThree.book(10, 40); // returns 2
MyCalendarThree.book(5, 15); // returns 3
MyCalendarThree.book(5, 10); // returns 3
MyCalendarThree.book(25, 55); // returns 3
Explanation: 
The first two events can be booked and are disjoint, so the maximum K-booking is a 1-booking.
The third event [10, 40) intersects the first event, and the maximum K-booking is a 2-booking.
The remaining events cause the maximum K-booking to be only a 3-booking.
Note that the last event locally causes a 2-booking, but the answer is still 3 because
eg. [10, 20), [10, 40), and [5, 15) are still triple booked.

 

Note:

• The number of calls to MyCalendarThree.book per test case will be at most 400.
• In calls to MyCalendarThree.book(start, end), start and end are integers in the range [0, 10^9].

 

這道題是之前那兩道題My Calendar II，My Calendar I的拓展，論壇上有人說這題不應該算是Hard類的，但實際上如果沒有之前那兩道題做鋪墊，直接上這道其實還是還蠻有難度的。這道題博主在做完之前那道，再做這道一下子就做出來了，因為用的就是之前那道My Calendar II的解法二，具體的講解可以參見那道題，反正博主寫完那道題再來做這道題就是秒解啊，參見代碼如下：

 

class MyCalendarThree {
public:
    MyCalendarThree() {}
    
    int book(int start, int end) {
        ++freq[start];
        --freq[end];
        int cnt = 0, mx = 0;
        for (auto f : freq) {
            cnt += f.second;
            mx = max(mx, cnt);
        }
        return mx;
    }
    
private:
    map<int, int> freq;
};

 

類似題目：

My Calendar II

My Calendar I

 

參考資料：

https://discuss.leetcode.com/topic/111978/java-c-clean-code

 

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