public class Solution
{
    /// <summary>
    /// O(n * log n)
    /// </summary>
    /// <param name="meetings"></param>
    /// <returns></returns>
    public int findMinimumMeetingRooms(List<Meeting> meetings)
    {
        meetings.Sort((x, y) => x.Start.CompareTo(y.Start));
        int rooms = 1;
        Meeting inProgress = meetings[0];
        for (int i = 1; i < meetings.Count; i++)
        {
            Meeting meeting = meetings[i];
            if (DoesIntersect(meeting, inProgress))
            {
                inProgress = FindIntersection(meeting, inProgress);
                rooms++;
            }
            else
            {
                inProgress = meeting;
            }
        }
        return rooms;
    }

    private bool DoesIntersect(Meeting meeting1, Meeting meeting2)
    {
        if ((meeting2.Start > meeting1.Start && meeting2.Start < meeting1.End)
            || (meeting1.Start > meeting2.Start && meeting1.Start < meeting2.End))
        {
            return true;
        }
        return false;
    }

    private Meeting FindIntersection(Meeting meeting1, Meeting meeting2)
    {
        return new Meeting(Math.Max(meeting1.Start, meeting2.Start), Math.Min(meeting1.End, meeting2.End));
    }
}