CODEWITHSUNDEEP
c#linq
Lucas Meijer
Lucas Meijer

Reputation: 4484

use LINQ to find which element "scores highest" on a certain function

If I have an 

IEnumerable<Something>

and a function that takes a Something, and return an int, how would I use LINQ to tell me which of my somethings gives the highest result when fed to my function?

Upvotes: 2

Views: 184

Answers (4)

Reza ArabQaeni
Reza ArabQaeni

Reputation: 4908

var something= List.Aggregate((p, q) => func(p) > func(q) ? p : q)

This aggregate is simple but call func method occured twice for max in per iteration, to avoid this:

var something=List.Select(p => new { something = p, call = func(p) })
                        .Aggregate((p, q) => p.call > q.call ? p : q).something;

Upvotes: 1

K2so
K2so

Reputation: 982

somethings.Max(p => p.intFunc());

Upvotes: -1

sehe
sehe

Reputation: 393613

You can use something like MaxBy from MoreLinq (or simply use MoreLinq):

public static TSource MaxBy<TSource, TKey>(this IEnumerable<TSource> source,
    Func<TSource, TKey> selector, IComparer<TKey> comparer)
{
    using (IEnumerator<TSource> sourceIterator = source.GetEnumerator())
    {
        if (!sourceIterator.MoveNext())
            throw new InvalidOperationException("Sequence was empty");
        TSource max = sourceIterator.Current;
        TKey maxKey = selector(max);

        while (sourceIterator.MoveNext())
        {
            TSource candidate = sourceIterator.Current;
            TKey candidateProjected = selector(candidate);
            if (comparer.Compare(candidateProjected, maxKey) > 0)
            {
                max = candidate;
                maxKey = candidateProjected;
            }
        }
        return max;
    }
}

Upvotes: 3

Mark Byers
Mark Byers

Reputation: 838896

You can use OrderByDescending:

Something result = yourEnumerable.OrderByDescending(x => f(x)).First();

Note that this results in a O(n log n) sort if you are using LINQ to Objects.

You could also use MaxBy from MoreLINQ:

Something result = yourEnumerable.MaxBy(x => f(x));

Upvotes: 2

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