Question

List:

List<int> list1 = new List<int>(){ 0, 1, 2, 3, 4, 5, 6 };

let’s say we want to reorder it. The beginning should be at number “2”

// 2,3,4,5,6,0,1

or at number 5

// 5,6,0,1,2,3,4

how do you do it with C#?

the reason: Imagine that you have an index of a given number in the List (number 3, index 3). You want to get the second number from the right – it’ll be 5.

Unfortunately, if the starting number is at the end of the List (numbers 5 and 6) – out of range exception will be thrown, because there’s no 7 and 8!

The idea is to reorder the List!

• We enter Nr. 5 – we get 0 (5,6,0).
• We enter Nr. 6 – we get 1 (6,0,1), etc.

or maybe there is some other (read – better) way to solve this problem?

Answer 1

You don’t need to reorder the list. You could get the number with the following function:

int GetNumber(List<int> list, int fromValue, int index) 
{
    return list[(list.IndexOf(fromValue) + index) % list.Count()];
}

You could call the function like this:

List<int> list1 = new List<int>(new[] { 0, 1, 2, 3, 4, 5, 6 });
int number = GetNumber(list1, 5, 2); // number = 0