How to write a program to find the permutations of a given string in C#(coding interview question)

I really feel challenged in solving this problem. Basically the term permutations means arranging in an unique order(I don't know anything more). I tried finding permutations on a piece of paper, quite easy to think and note them down. Then I tried to write a program for it to find permutations for as many character as we like. I figured to solve the problem in the following way. Hope it will help you learn something. There is fiddle link below. Run it and know how it works.

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using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
    public static void Main(string[] args)
    {
        var stringText = "ABCD";
        var possibilities = GetPossibilities(stringText);
        Console.WriteLine("The permutations of *{0}* are as shown below:", stringText);
        foreach (var pos in possibilities)
        {
            Console.WriteLine(">>>>>>>>>>>>>>" + pos + "<<<<<<<<<<<<<<");
        }
    }

    private static List<string> GetPossibilities(string text)
    {
        bool reached = false;
        List<string> possibleStrings = new List<string>();
        List<int> possibleInts = new List<int>();
        var textArray = text.ToArray();
        string prev = string.Empty;
        string dummy = string.Empty;
        int preIndexNum = 1;
        while (!reached)
        {
            var indexes = GetDigitsList(preIndexNum);
            foreach (var index in indexes)
            {
                dummy = dummy + textArray[index - 1];
            }
            bool isPermutation = CheckPermutation(dummy, text);
            if (isPermutation)
            {
                possibleStrings.Add(dummy);
                possibleInts.Add(preIndexNum);
            }
            dummy = string.Empty;
            reached = checkReached(preIndexNum, textArray.Length);
            preIndexNum = GetNumberBasedOnTextLength(textArray.Length, preIndexNum);
        }
        var distinctStrings = possibleStrings.Distinct().ToList();
        return distinctStrings;
    }


    private static bool CheckPermutation(string dummy, string text)
    {
        if (dummy.Count() != text.Length)
            return false;
        else
        {
            foreach (var t in dummy)
            {
                if (dummy.Count(x => x == t) == text.Count(x => x == t))
                    continue;
                else
                    return false;
            }
            return true;
        }
    }

    private static int GetNumberBasedOnTextLength(int length, int number)
    {
        var digitsList = GetDigitsList(number);
        digitsList.Reverse();
        var digitsArray = digitsList.ToArray();
        var dummyIntList = new int[digitsArray.Length + 1];
        for (int i = 0; i < digitsArray.Length; i++)
        {
            dummyIntList[i] = digitsArray[i];
        }
        for (int i = 0; i < dummyIntList.Length; i++)
        {
            if (dummyIntList[i] < length)
            {
                dummyIntList[i] = dummyIntList[i] + 1;
                break;
            }
            if (dummyIntList[i] == length)
            {
                for (int j = i; j < dummyIntList.Length; j++)
                {
                    if (dummyIntList[j] < length)
                    {
                        dummyIntList[j] = dummyIntList[j] + 1;
                        break;
                    }
                    else
                        dummyIntList[j] = 1;
                }
                break;
            }
        }
        var list = dummyIntList.ToList();
        list.Reverse();
        number = GenrateNumber(list.ToArray());
        return number;
    }
    private static int GenrateNumber(int[] digitsArray)
    {
        int sum = 0;
        for (int i = 0; i < digitsArray.Length; i++)
        {
            if (digitsArray[i] == 0)
                continue;
            sum = sum * 10 + digitsArray[i];
        }
        return sum;
    }
    private static List<int> GetDigitsList(int number)
    {
        List<int> digitsList = new List<int>();
        while (number > 0)
        {
            digitsList.Add(number % 10);
            number = number / 10;
        }
        digitsList.Reverse();
        return digitsList;
    }
    private static bool checkReached(int preIndexNum, int length)
    {
        var digitsList = GetDigitsList(preIndexNum);
        if (digitsList.Count() == length)
        {
            foreach (var digit in digitsList)
            {
                if (digit < length)
                    return false;
            }
            return true;
        }
        else
        {
            return false;
        }
    }
}

To know the how the code works check this link: PermutationsOfString(.net fiddle)

using System; using System.Collections.Generic; using System.Linq; namespace StringPermutations { public class Program { public static void Main(string[] args) { Console.Write("Enter a string to permutate: "); var stringText = Console.ReadLine(); var possibilities = GetPossibilities(stringText); foreach (var pos in possibilities) { //if(pos.Length == stringText.Length) // System.IO.File.AppendAllText(@"C:\Users\Snovasys7\Desktop\test.txt", pos + Environment.NewLine); Console.WriteLine(pos); } Console.ReadKey(); } private static List GetPossibilities(string text) { bool reached = false; List possibleStrings = new List(); List possibleInts = new List(); var textArray = text.ToArray(); string prev = string.Empty; string dummy = string.Empty; int preIndexNum = 1; while (!reached) { var indexes = GetDigitsList(preIndexNum); foreach (var index in indexes) { dummy = dummy + textArray[index - 1]; } bool isPermutation = CheckPermutation(dummy, text); if (isPermutation) { possibleStrings.Add(dummy); possibleInts.Add(preIndexNum); } dummy = string.Empty; reached = checkReached(preIndexNum, textArray.Length); preIndexNum = GetNumberBasedOnTextLength(textArray.Length, preIndexNum); } //var ints = possibleInts.Distinct(); //foreach (var pos in ints) //{ // System.IO.File.AppendAllText(@"C:\Users\Snovasys7\Desktop\ints.txt", pos + Environment.NewLine); //} //return possibleStrings; var distinctStrings = possibleStrings.Distinct().ToList(); return distinctStrings; } private static bool CheckPermutation(string dummy, string text) { if (dummy.Count() != text.Length) return false; else { foreach (var t in dummy) { if (dummy.Count(x => x == t) == text.Count(x => x == t)) continue; else return false; } return true; } } private static int GetNumberBasedOnTextLength(int length, int number) { var digitsList = GetDigitsList(number); digitsList.Reverse(); var digitsArray = digitsList.ToArray(); var dummyIntList = new int[digitsArray.Length + 1]; for (int i = 0; i < digitsArray.Length; i++) { dummyIntList[i] = digitsArray[i]; } for (int i = 0; i < dummyIntList.Length; i++) { if (dummyIntList[i] < length) { dummyIntList[i] = dummyIntList[i] + 1; break; } if (dummyIntList[i] == length) { for (int j = i; j < dummyIntList.Length; j++) { if (dummyIntList[j] < length) { dummyIntList[j] = dummyIntList[j] + 1; break; } else dummyIntList[j] = 1; } break; } } var list = dummyIntList.ToList(); list.Reverse(); number = GenrateNumber(list.ToArray()); return number; } private static int GenrateNumber(int[] digitsArray) { int sum = 0; for (int i = 0; i < digitsArray.Length; i++) { if (digitsArray[i] == 0) continue; sum = sum * 10 + digitsArray[i]; } return sum; } private static List GetDigitsList(int number) { List digitsList = new List(); while (number > 0) { digitsList.Add(number % 10); number = number / 10; } digitsList.Reverse(); return digitsList; } private static bool checkReached(int preIndexNum, int length) { var digitsList = GetDigitsList(preIndexNum); if (digitsList.Count() == length) { foreach (var digit in digitsList) { if (digit < length) return false; } return true; } else { return false; } } } }