/// http://stackoverflow.com/questions/35951415

using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static string A = "A";

    public static string B = "B";

    public static string C = "C";

    public static string NULL = "null";

    public static void Main()

    {   

        var lo = new LO();

        lo.Add(new OB{A});

        lo.Add(new OB{B});

        lo.DisplayResult();

​

        lo.Clear();

        lo.Add(new OB{A});

        lo.Add(new OB{NULL});

        lo.Add(new OB{B});

        lo.DisplayResult();

​

        lo.Clear();

        lo.Add(new OB{A});

        lo.Add(new OB{NULL});

        lo.Add(new OB{NULL});

        lo.Add(new OB{NULL});

        lo.Add(new OB{NULL});

        lo.Add(new OB{B});

        lo.DisplayResult();

        lo.Clear();

        lo.Add(new OB{A});

        lo.Add(new OB{A,B});

        lo.Add(new OB{B});

        lo.DisplayResult();

​

        lo.Clear();

        lo.Add(new OB{A});

        lo.Add(new OB{NULL});

        lo.Add(new OB{A});

        lo.DisplayResult();

​

        lo.Clear();

        lo.Add(new OB{A});

        lo.Add(new OB{A,B});

        lo.Add(new OB{A});

        lo.DisplayResult("Why is this not a transition but an exception?");

​

​

        lo.Clear();

        lo.Add(new OB{A});

        lo.Add(new OB{A,NULL});

        lo.Add(new OB{A,NULL,NULL});

        lo.Add(new OB{A});

        lo.DisplayResult("<A,NULL> and <A,NULL,NULL> are considered equal as per your second comment.");

​

        lo.Clear();

        lo.Add(new OB{A});

        lo.Add(new OB{A,B,NULL,C});

        lo.Add(new OB{A});

        lo.DisplayResult("As per your first comment");

​

        lo.Clear();

        lo.Add(new OB{A});

        lo.Add(new OB{A,B});

        lo.Add(new OB{B,A});

        lo.Add(new OB{A});

        lo.DisplayResult("Second and third OB are equal as per your first comment");

​

        lo.Clear();

        lo.Add(new OB{A});

        lo.Add(new OB{NULL,A});

        lo.Add(new OB{B});

        lo.DisplayResult();

​

        lo.Clear();

        lo.Add(new OB{A});

        lo.Add(new OB{A,B,C});

        lo.Add(new OB{B});

        lo.DisplayResult("Why is this not a transition as per your fourth comment?");

    }

}

​

// list of objects (LO) = list<OB>

public class LO : List<OB>

{

    public void DisplayResult(string message = null)

    {

        Console.WriteLine("{0} : {1}",this,CountTransitions());

        if(message != null)

        {

            Console.WriteLine(message);

        }

        Console.WriteLine();

    }

​

    private int CountTransitions()

    {

        if(this.Any()== false || this.Count == 1) return 0;

        var first = this.FirstOrDefault();

        var last = this.LastOrDefault();

        // first OB and last OB must have exactly one element.

        if(first.Count != 1 || last.Count != 1) return 0;

        var transitions = 0;

        for(var i = 0; i < this.Count - 1; i++)

        {

            // when current OB and next OB are not the same, it is a transition

            transitions = IsTransition(this[i],this[i+1]) ? transitions + 1 : transitions;

        }

        return transitions;

    }

    private bool IsTransition(OB lhs, OB rhs)

    {

        var lhsSet = new SortedSet<String>(lhs);

        var rhsSet = new SortedSet<String>(rhs);

        return lhsSet.SetEquals(rhsSet) == false;

    }

​

    public override string ToString()

    {

        return String.Join(" -> ", this.Select(x => x.ToString()));

    }

}

​

// objects (OB) = list<int?>

public class OB : List<String>

{

    public override String ToString()

    {

        return String.Format("[{0}]", String.Join(",", this));

    }

}