How to find a sub-list of two consecutive items in a list using Linq

Question

Suppose that we have a list of strings like

\"A\", \"B\", \"C\", \"D\", \"E\", \"F\"

Now I\'d like to search for a sub-list of

Answer 1

I didn't see a shorter solution than yours. But I think the solution you propose only works if first string doesn't appear twice in the list. For example, if the list was:

"A", "D", "B", "C", "D", "E", "F"

I think your proposal will not work because first FindIndex will return the index of the first "D", which is not followed by "E".

A posible alternative could be (should be tested to be sure):

    int index=-1;
    Parallel.For(0, list.Count - 1, i =>
    {
      if (list[i] == "D" && list[i + 1] == "E")
      {
          Interlocked.Exchange(ref index, i);
      }
    }); 
//after the loop, if index!=-1, sublist was found and starts at index position

Not shorter, of course, but can be faster if list is very large, because using Parallel.For. A limitation is that if the sublist appears several times, you can obtain the index of any of them (not necessarily the first one).