Best sequence using LINQ

I have ordered list like in example 

var someList = new List<int>{1,1,2,3,5,2,1,3,7,1};

I want to select by using LINQ best(highest sum) sequence of 3 numbers. In this case answer is 3,7,1 or 1,3,7. Is that possible without change order or sorting? I have an idea how to do this without LINQ, but I just wanna know to do with LINQ

Jon Skeet
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You can use Skip/Zip to end up with triples. For example:

var triples = list.Zip(list.Skip(1).Zip(list.Skip(2), (b, c) => new { b, c }),
                       (a, bc) => new { a, bc.b, bc.c });

(That may have some errors - I haven't tested it yet.)

You can then order those triples pretty easily:

var orderedTriples = triples.OrderByDescending(t => t.a + t.b + t.c);

If you're using the triples in multiple contexts, you might want to write an extension method to use Tuple<,,> instead:

public static IEnumerable<Tuple<T, T, T>> InTriples<T>(this IEnumerable<T> source)
{
    // Or potentially write custom code to do this. It wouldn't be too hard...
    return source.Zip(list.Skip(1).Zip(list.Skip(2), (b, c) => new { b, c }),
                      (a, bc) => Tuple.Create(a, bc.b, bc.c));
}

As for whether LINQ is suitable for this - having the InTriples method generally available means that the rest of the code becomes pretty simple. Using Skip/Zip isn't going to be terribly efficient, but once you've got the code going using that, you can easily rewrite the InTriples method to use an iteerator block instead.

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