Remove List Elements that appear more than Once In Place

Question

There is a similar question posted, but I do not have the rep to ask a follow-up question in that thread :(

That question and solution is HERE.

If I have a Lis

Answer 1

So, if you can have a new list, then this is the easiest way to do it:

var source = new List() { 4, 5, 7, 3, 5, 4, 2, 4 };

var result =
    source
        .GroupBy(x => x)
        .Where(x => !x.Skip(1).Any())
        .Select(x => x.Key)
        .ToList();

This gives:

{ 7, 3, 2 }

If you want to remove the values from the original source, then do this:

var duplicates =
    new HashSet(
        source
            .GroupBy(x => x)
            .Where(x => x.Skip(1).Any())
            .Select(x => x.Key));

source.RemoveAll(n => duplicates.Contains(n));