How to get all subsets of an array?

Question

Given an array: [dog, cat, mouse]

what is the most elegant way to create:

[,,]
[,,mouse]
[,cat,]
[,cat,mouse]
[dog,,]
[dog,,mouse]
[dog,         


        

Answer 1

static IEnumerable> GetSubsets(IList set)
{
    var state = new BitArray(set.Count);
    do
        yield return Enumerable.Range(0, state.Count)
                               .Select(i => state[i] ? set[i] : default(T));
    while (Increment(state));
}

static bool Increment(BitArray flags)
{
    int x = flags.Count - 1; 
    while (x >= 0 && flags[x]) flags[x--] = false ;
    if (x >= 0) flags[x] = true;
    return x >= 0;
}

Usage:

foreach(var strings in GetSubsets(new[] { "dog", "cat", "mouse" }))
    Console.WriteLine(string.Join(", ", strings.ToArray()));