Removing alternate elements in a List

Question

What is the most efficient way to remove alternate (odd indexed or even indexed) elements in an List without using a place holder list variable?

A

Answer 1

Just for consideration of a solution that creates a new list, with a list old you could do this:

var newList = old.Where((_, i) => i%2 != 0).ToList();

or, obviously

var newList = l.Where((_, i) => i%2 == 0).ToList();

depending which alternation you choose.

EDIT

The answer is quite a bit quicker. If you read something else here, it's because I measured on a weekend and weekend's brain is funny. :( The closure solution is about 40% quicker while the answer is app. 2 orders of magnitude faster. I suppose it will really depend how big your list becomes!