Question

I asked this question in the chat room. but no answer so i am posting the question here.

The question is, for example take the word abcd

it has 4 charcters. by adding the ‘ . ‘ in between the characters you can write it as a.b.c.d

rules
can use only 1 dot between characters
can use multiple dots in the word
Edit: there can be characters without ‘ . ‘ in between them. eg (ab or abcd)
cannot use dot at the beginning or end of the word ie .abcd or abcd. are false

some of the answers
a.b.c.d
a.bcd
ab.cd
abc.d
a.b.cd
a.bc.d
ab.c.d
abc.d

how many word are possible to make. how to write a program to find it in c# ?

Edit
how to display each possible word ?

Answer 1

You can do it recursively.

All possible combinations of (abcd) are:

a + . + all combinations of (bcd)
ab + . + all combinations of (cd)
abc + . + all combinations of (d)
abcd

Code:

public static IEnumerable<string> GetCombinations(string str) {
  for (int i = 1; i < str.Length; i++) {
    foreach (string s in GetCombinations(str.Substring(i))) {
      yield return str.Substring(0, i) + "." + s;
    }
  }
  yield return str;
}

Usage:

foreach (string s in GetCombinations("abcd")) Console.WriteLine(s);