INTERVIEW JOB CODING TASKS – Calculate permutations1 min read

Today we are going to continue with interview coding tasks.

I really do hope this, solved, coding task is going to help you during your interview.

Task: Depending on input value i.e. (123) create all permutations i.e:(123,213,231,132,312,321)


private static void Main(string[] args)
public static void WritePermutations()
	var permutations = GetPermutations("123");

	foreach (var permutation in permutations)
public static List<string> GetPermutations(string inputString)
	return IsPermutated(inputString, out var permutations, out var list) ? list : ListOfPermutations(inputString, permutations);
private static bool IsPermutated(string inputString, out List<string> permutations, out List<string> list)
            permutations = new List<string>();
            list = null;

            if (inputString == null) return true;
            if (inputString.Length != 0) return false;
                list = permutations;
                return true;

private static List<string> ListOfPermutations(string inputString, List<string> permutations)
	var firstCharacter = inputString[0];
	var remainder = inputString.Substring(1);
	var words = GetPermutations(remainder);
	foreach (var word in words)
		for (var i = 0; i <= word.Length; i++)
			permutations.Add(InsertCharacterAt(word, firstCharacter, i));

	return permutations;
public static string InsertCharacterAt(string word, char character, int i)
  var start = word.Substring(0, i);
  var end = word.Substring(i);
   return $"{start}{character}{end}";


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