Question

I have integer list in C#. I need a method that, to give startIndex and step parameters and to take sublists from that. When reach to end, cross to begin of list. like circle

public List<int> GetSomeInt(List<int> mainList, int startIndex, int step )
{
  ...
}

For example, list elements are 4, 2, 85, 6, 7, 89, 1, 0, 36, 47, 11, 75. I give startIndex=3 and step=5 to method and I get so results:

result1 - 6, 7, 89, 1, 0
result2 - 36, 47, 11, 75, 4
result3 - 2, 85, 6, 7, 89, 1
result4 - 0, 36, 47, 11, 75
result5 - 4, 2, 85, 6, 7
result6 - 89, 1, 0, 36, 47
........................

How I get so successive sub-elements of list?

Answer 1

You could use Queue to do round shift then get the result by LINQ Take
:

public static List<List<int>> GetSomeInt(List<int> mainList, 
                                         int startIndex, int step)
{
    var queue = new Queue<int>();
    mainList.ForEach(queue.Enqueue);

    Enumerable.Range(0, startIndex)
        .ToList()
        .ForEach(i => queue.Enqueue(queue.Dequeue()));

    var result = new List<List<int>>();

    while (true)
    {
        var list = queue.Take(step).ToList();
        list.ForEach(i => queue.Enqueue(queue.Dequeue()));

        if (result.Any(l => l.All(list.Contains)))
            break;

        result.Add(list.ToList());
    }

    return result;
}