732. My Calendar III (Hard)
https://leetcode.com/problems/my-calendar-iii/
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.
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 most400
. - In calls to
MyCalendarThree.book(start, end)
,start
andend
are integers in the range[0, 10^9]
.
Solutions
class MyCalendarThree {
// Also, you can use Map<Integer, List<Integer>> to keep all the specific books in this range
// assume the problem requires which ranges contain most books and return them if found.
Map<Integer, Integer> delta = new TreeMap();
public int book(int start, int end) {
// You don't have to know which book begins from 'start', the number of books will
// be sufficient.
delta.put(start, delta.getOrDefault(start, 0) + 1);
// The only thing you should know is how many books ends here, no the specific books.
delta.put(end, delta.getOrDefault(end, 0) - 1);
int max = 0;
int active = 0;
// For TreeMap, keys are sorted.
for (int d : delta.values()) {
active += d;
if (active > max) {
max = active;
}
}
return max;
}
}