Question

i want to pick the integer combinations using a single integer,
like I have a number 1234.. Now what i want is: 1,2,3,4,12,23,34,123,234,1234

Kindly help..??

Answer 1

If I understood you right, you want all substrings of a given string (in this case the number 1234). So, for a string of length n there are n substrings of length 1, n − 1 substrings of length 2, etc. until one substring of length n.

Given that you can easily solve this with two nested loops, e.g.:

public static IEnumerable<int> Foo(int x) {
  string s = x.ToString();
  for (int length = 1; length <= s.Length; length++) {
    for (int i = 0; i + length < s.Length; i++) {
      yield return int.Parse(s.Substring(i, length));
    }
  }
}

(Untested and there are likely fencepost errors, but you get the idea.)