732. My Calendar III

732-my-calendar-3.java

// solution to: 732. My Calendar III https://leetcode.com/problems/my-calendar-iii/
class MyCalendarThree {

    private final Comparator<Pos> comparator = Comparator.<Pos>comparingInt(p -> p.pos)
        .thenComparing((p1, p2) -> {
            if (p1.mark == p2.mark) return Integer.compare(p1.hashCode(), p2.hashCode());
            if (p1.mark == Mark.END) return -1;
            return 1;
        });
    private final SortedSet<Pos> marks = new TreeSet<>(comparator);

    static class Pos {
        final int pos;
        final Mark mark;

        Pos(int pos, Mark mark) {
            this.pos = pos;
            this.mark = mark;
        }
    }

    enum Mark {
        START,
        END
    }

    public int book(int start, int end) {
        marks.add(new Pos(start, Mark.START));
        marks.add(new Pos(end, Mark.END));

        int count = 0;
        int max = 0;
        for (Pos pos : marks) {
            if (pos.mark == Mark.START) {
                count++;
                max = Math.max(max, count);
            } else {
                count--;
            }
        }
        return max;
    }
}