Algorithm to detect overlapping periods [duplicate]

Answer 1

Try this. This method will determine if (two) date spans are overlapping, regardless of the ordering of the method's input arguments. This can also be used with more than two date spans, by individually checking each date span combination (ex. with 3 date spans, run span1 against span2, span2 against span3, and span1 against span3):

public static class HelperFunctions
{
    public static bool AreSpansOverlapping(Tuple span1, Tuple span2, bool includeEndPoints)
    {
        if (span1 == null || span2 == null)
        {
            return false;
        }
        else if ((new DateTime[] { span1.Item1, span1.Item2, span2.Item1, span2.Item2 }).Any(v => v == DateTime.MinValue))
        {
            return false;
        }
        else
        {
            if (span1.Item1 > span1.Item2)
            {
                span1 = new Tuple(span1.Item2, span1.Item1);
            }
            if (span2.Item1 > span2.Item2)
            {
                span2 = new Tuple(span2.Item2, span2.Item1);
            }

            if (includeEndPoints)
            {
                return 
                ((
                    (span1.Item1 <= span2.Item1 && span1.Item2 >= span2.Item1) 
                    || (span1.Item1 <= span2.Item2 && span1.Item2 >= span2.Item2)
                ) || (
                    (span2.Item1 <= span1.Item1 && span2.Item2 >= span1.Item1) 
                    || (span2.Item1 <= span1.Item2 && span2.Item2 >= span1.Item2)
                ));
            }
            else
            {
                return 
                ((
                    (span1.Item1 < span2.Item1 && span1.Item2 > span2.Item1) 
                    || (span1.Item1 < span2.Item2 && span1.Item2 > span2.Item2)
                ) || (
                    (span2.Item1 < span1.Item1 && span2.Item2 > span1.Item1) 
                    || (span2.Item1 < span1.Item2 && span2.Item2 > span1.Item2)
                ) || (
                    span1.Item1 == span2.Item1 && span1.Item2 == span2.Item2
                ));
            }
        }
    }
}

Test:

static void Main(string[] args)
{  
    Random r = new Random();

    DateTime d1;
    DateTime d2;
    DateTime d3;
    DateTime d4;

    for (int i = 0; i < 100; i++)
    {
        d1 = new DateTime(2012,1, r.Next(1,31));
        d2 = new DateTime(2012,1, r.Next(1,31));
        d3 = new DateTime(2012,1, r.Next(1,31));
        d4 = new DateTime(2012,1, r.Next(1,31));

        Console.WriteLine("span1 = " + d1.ToShortDateString() + " to " + d2.ToShortDateString());
        Console.WriteLine("span2 = " + d3.ToShortDateString() + " to " + d4.ToShortDateString());
        Console.Write("\t");
        Console.WriteLine(HelperFunctions.AreSpansOverlapping(
            new Tuple(d1, d2),
            new Tuple(d3, d4),
            true    //or use False, to ignore span's endpoints
            ).ToString());
        Console.WriteLine();
    }

    Console.WriteLine("COMPLETE");
    System.Console.ReadKey();
}