C# Collection - Order by an element (Rotate)

Question

I have an IEnumerable collection. Lets say it contains 5 points (in reality it is more like 2000)

I want to order this collection so that a spe

Answer 1

The naive implementation using linq would be:

IEnumerable x = new[] { 1, 2, 3, 4 };
var tail = x.TakeWhile(i => i != 3);
var head = x.SkipWhile(i => i != 3);
var combined = head.Concat(tail); // is now 3, 4, 1, 2

What happens here is that you perform twice the comparisons needed to get to your first element in the combined sequence. The solution is readable and compact but not very efficient. The solutions described by the other contributors may be more efficient since they use special data structures as arrays or lists.