getting repeated combinations using LINQ

Question

i have two numbers 1,2 in one array.Now i want to generate all the possible combinations of arrays(of size=5) like

1,2,0,0,0 || 2,1,0,0,0 || 1,0,2,0,0 . . . . .

I tried to write a recursive function but its not working

Now I want to solve this using LINQ because the code will be considerably small.

Please help me

see [this question](http://stackoverflow.com/questions/774457/combination-generator-in-linq) or [this one](http://stackoverflow.com/questions/1119699/how-to-generate-combinations-of-elements-of-a-listt-in-net-4-0) — voidengine, Jan 07 '12 at 13:53

Sergey Kalinichenko · Accepted Answer · 2012-01-07T14:25:32.830

LINQ is excellent for searching; it's much worse at generating, so it is a wrong tool for the job. So is recursion (although it is a better choice than LINQ). What you need is two nested loops, like this:

var elements = new [] {1, 2};
for (var i = 0 ; i != 5 ; i++) {
    for (int j = 0 ; j != 5 ; j++) {
        if (i == j) continue;
        var data = new int[5];
        data[i] = elements[0];
        data[j] = elements[1];
        ProcessCombination(data);
    }
}

Here is what the code does: at each iteration of the inner loop it places the first and the second element from the elements array at distinct positions i and j. Nested loops go from 0 to 5, making sure all position combinations are covered.

@SuryaKLSV I added an explanation to the answer. – Sergey Kalinichenko Jan 07 '12 at 14:25 — Sergey Kalinichenko, Jan 07 '12 at 14:25

score -1 · Answer 2 · answered Jan 07 '12 at 13:50

You could use something like this:

  public static IEnumerable<IEnumerable<T>> Permute<T>(IEnumerable<T> list)
  {
            if (list.Count() == 1)
                return new List<IEnumerable<T>> { list };

            return list.Select((a, i1) => Permute(
                            list.Where((b, i2) => i2 != i1)).Select(
                                  b => (new List<T> { a }).Union(b))
                            ).SelectMany(c => c);
   };

.....

var result = Permute(new int[]{1,2,0,0,0});

-1 Besides not giving a reference to original code http://stackoverflow.com/a/5757434/932418', It doesn't work for `new int[]{1,2,0,0,0}` (`multiple 0s`) — L.B, Jan 07 '12 at 15:07

getting repeated combinations using LINQ

2 Answers2