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Set of maximum independent subsets using C # generator

I want to find all subsets of a given set that are mutually exclusive and contain as many elements of the subset as possible. If the user defines an exclusivity value:

bool exclusion<T>(T a, T b)

where at least exclusion(a, b) == exclusion(b, a).

And exclusion(a, b) == trueguaranteed ifa.Equals(b) == true

My code is as follows:

public static HashSet<HashSet<T>> MutuallyExclusive<T>(this IEnumerable<T> available, Func<T, T, bool> exclusion) {
    HashSet<HashSet<T>> finished = new HashSet<HashSet<T>>(new HashSetEquality<T>());
    Recursion<T>(available, new HashSet<T>(), finished, exclusion);
    return finished;
}

private static void Recursion<T>(IEnumerable<T> available, HashSet<T> accepted, HashSet<HashSet<T>> finished, Func<T, T, bool> exclusion) {
    if (!available.Any())
        finished.Add(accepted);
    else
        foreach (T a in available)
            Recursion<T>(available.Where(b => !exclusion(a, b)), new HashSet<T>(accepted) { a }, finished, exclusion);
}

private class HashSetEquality<T> : IEqualityComparer<HashSet<T>> {
    public bool Equals(HashSet<T> x, HashSet<T> y) {
        if (x.Count != y.Count)
            return false;
        return x.All(t => y.Contains(t));
    }

    public int GetHashCode(HashSet<T> obj) {
        return obj.Aggregate(0, (i, t) => i ^ t.GetHashCode());
    }
}

Is there a way to turn this code into an iterator that moves along the accepted values ​​one by one?

Edit:

It seems I was a little incomprehensible in my question, sorry. I really was looking for a generator for debuting performance. So that every time you call it, only the next accepted set is calculated

+5
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2 answers

, , finished.Add(), true.

- , . , :

public static IEnumerable<HashSet<T>> MutuallyExclusive<T>(
    this IEnumerable<T> available, Func<T, T, bool> exclusion)
{
    var finished = new HashSet<HashSet<T>>(new HashSetEquality<T>());
    return Recursion<T>(available, new HashSet<T>(), finished, exclusion);
}

private static IEnumerable<HashSet<T>> Recursion<T>(
    IEnumerable<T> available, HashSet<T> accepted, HashSet<HashSet<T>> finished,
    Func<T, T, bool> exclusion)
{
    if (!available.Any())
    {
        if (finished.Add(accepted))
            yield return finished;
    }
    else
        foreach (T a in available)
        {
            var results = Recursion<T>(
                available.Where(b => !exclusion(a, b)),
                new HashSet<T>(accepted) { a }, finished, exclusion);

            foreach (var set in results)
                yield return set;
        }
}

, , , .

, . , finished, .

+2

return finished;

foreach (HashSet<T> set in finished)
    yield return set;

( , ?), MutuallyExclusive HashSet<HashSet<T>> IEnumerable<HashSet<T>>. , MutuallyExclusive :

public static IEnumerable<HashSet<T>> MutuallyExclusive<T>(this IEnumerable<T> available, Func<T, T, bool> exclusion)
{
    HashSet<HashSet<T>> finished = new HashSet<HashSet<T>>(new HashSetEquality<T>());
    Recursion<T>(available, new HashSet<T>(), finished, exclusion);
    foreach (HashSet<T> set in finished)
        yield return set;
}
-1

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