My Calendar I

Implement aMyCalendarclass to store your events. A new event can be added if adding the event will not cause a double booking.

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

Adouble bookinghappens when two events have some non-empty intersection (ie., there is some time that is common to both events.)

For each call to the methodMyCalendar.book, returntrueif the event can be added to the calendar successfully without causing a double booking. Otherwise, returnfalseand do not add the event to the calendar.

Your class will be called like this:

MyCalendar cal = new MyCalendar();

MyCalendar.book(start, end)

Example 1:

MyCalendar();
MyCalendar.book(10, 20); // returns true
MyCalendar.book(15, 25); // returns false
MyCalendar.book(20, 30); // returns true

Explanation:

The first event can be booked.  The second can't because time 15 is already booked by another event.
The third event can be booked, as the first event takes every time less than 20, but not including 20.

Note:

• The number of calls to MyCalendar.book

  per test case will be at most 1000.

• In calls to MyCalendar.book(start, end), start and end are integers in the range [0, 10^9].

Solution

Naive ArrayList Implementation

O(N) time for each book() operation, N is existing booking events in the list

O(N) space

75 ms, faster than 95.89%

class MyCalendar {
    List<int[]> calendar;

    public MyCalendar() {
        calendar = new ArrayList<>();
    }

    public boolean book(int start, int end) {
        for (int[] iv: calendar) {
            if (iv[0] < end && iv[1] > start) {
                return false;
            }
        }
        calendar.add(new int[] {start, end});
        return true;
    }
}

/**
 * Your MyCalendar object will be instantiated and called as such:
 * MyCalendar obj = new MyCalendar();
 * boolean param_1 = obj.book(start,end);
 */

TreeMap -- Self-Balanced Binary Tree Implementation

每次寻找start 对应的floorKey, ceilingKey，比较start，end以及相邻两个区间的起始终止点，来判断是否有可行的插入区间。

Time: O(logN). Where NN is the number of events booked. For each new event, we search that the event is legal in O(logN) time, then insert it in O(logN) time.

Space: O(N)

class MyCalendar {
    TreeMap<Integer, Integer> calendar;

    public MyCalendar() {
        calendar = new TreeMap<>();
    }

    public boolean book(int start, int end) {
        Integer prev = calendar.floorKey(start);
        Integer next = calendar.ceilingKey(start);
        if ((prev == null || start >= calendar.get(prev)) && (next == null || end <= next)) {

            calendar.put(start, end);
            return true;
        }
        return false;
    }
}

/**
 * Your MyCalendar object will be instantiated and called as such:
 * MyCalendar obj = new MyCalendar();
 * boolean param_1 = obj.book(start,end);
 */