Question

I need a C# function that takes 2 strings as an input and return an array of all possible combinations of strings.

private string[] FunctionName(string string1, string string2) 
{
    //code
}

The strings input will be in the following format:

string1: basement

string2: a*fa

Now what I need is all combinations of possible strings using the characters in String2 (ignoring the * symbols), and keeping them in the same character position like this:

baaement, baaefent, baaefena, basefent, basemena, etc.

EDIT:
This is not homework. I need this function for a piece of a program I am doing.
The following is the code I have so far but it has some bugs.

static List<string> combinations = new List<string>();

static void Main(string[] args)
{
    //include trimming of input string
    string FoundRes = "incoming";
    string AltRes = "*2*45*78";
    List<int> loc = new List<int>();
    string word = "";


    for (int i = 0; i < AltRes.Length; i++)
    {
        if (AltRes[i] != '*')
        {
            loc.Add(i);
            word += AltRes[i];
        }
    }

    generate(word);
    string[] aaa = InsertSymbol(FoundRes, loc.ToArray(), AltRes, combinations);

    Console.WriteLine("input string: " + FoundRes);
    Console.WriteLine("Substitute string: " + AltRes);

    Console.WriteLine("============Output============");


    for (int j = 0; j < aaa.Length; j++)
    {

        Console.WriteLine(aaa[j]);
    }
    Console.ReadKey();
}//

private static void generate(string word)
{
    // Add this word to combination results set
    if (!combinations.Contains(word))
        combinations.Add(word);

    // If the word has only one character, break the recursion
    if (word.Length == 1)
    {
        if (!combinations.Contains(word))
            combinations.Add(word);
        return;
    }

    // Go through every position of the word
    for (int i = 0; i < word.Length; i++)
    {
        // Remove the character at the current position
        // call this method with the String
        generate(word.Substring(0, i) + word.Substring(i + 1));
    }
}//

private static string[] InsertSymbol(string orig, int[] loc, string alternative, List<string> Chars)
{
    List<string> CombinationsList = new List<string>();
    string temp = "";
    for (int i = 0; i < Chars.Count; i++)
    {
        temp = orig;
        for (int j = 0; j < Chars[i].Length; j++)
        {
            string token = Chars[i];

            if (alternative.IndexOf(token[j]) == loc[j])
            {
                temp = temp.Remove(loc[j], 1);
                temp = temp.Insert(loc[j], token[j].ToString());

                //     int pos = sourceSubst.IndexOf(token[j]);
                //     sourceSubst = sourceSubst.Remove(pos, 1);
                //     sourceSubst = sourceSubst.Insert(pos, ".");
            }
            else
            {
                temp = temp.Remove(alternative.IndexOf(token[j]), 1);
                temp = temp.Insert(alternative.IndexOf(token[j]), token[j].ToString());
            }
        }
        CombinationsList.Add(temp);
    }
    return CombinationsList.ToArray();
}//

Answer 1

It does sound like homework. As a suggestion, I would ignore the first parameter and focus on getting all possible permutations of the second string. What’s turned off, what’s turned on, etc. From that list, you can easily come up with a method of swapping out characters of the first string.

On that note, I’m in the uncomfortable position of having a function ready to go but not wanting to post it because of the homework implication. I’d sure love for somebody to review it, though! And technically, there’s two functions involved because I just happened to already have a generic function to generate subsets lying around.

Edit: OP says it isn’t homework, so here is what I came up with. It has been refactored a bit since the claim of two functions, and I’m more than open to criticism.

using System;
using System.Collections.Generic;
using System.Text;

class Program
{
    static void Main()
    {
        string original = "phenomenal";
        string pattern = "*xo**q*t**";

        string[] replacements = StringUtility.GetReplacementStrings(original, pattern, true);

        foreach (string replacement in replacements)
            Console.WriteLine(replacement);

        Console.Read();
    }

    public static class StringUtility
    {
        public static string[] GetReplacementStrings(string original, string pattern, bool includeOriginal)
        {
            // pattern and original might not be same length
            int maxIndex = Math.Max(original.Length, pattern.Length);

            List<int> positions = GetPatternPositions(pattern, maxIndex, '*');
            List<int[]> subsets = ArrayUtility.CreateSubsets(positions.ToArray());
            List<string> replacements = GenerateReplacements(original, pattern, subsets);

            if (includeOriginal)
                replacements.Insert(0, original);

            return replacements.ToArray();
        }

        private static List<string> GenerateReplacements(string original, string pattern, List<int[]> subsets)
        {
            List<string> replacements = new List<string>();
            char[] temp = new char[original.Length];

            foreach (int[] subset in subsets)
            {
                original.CopyTo(0, temp, 0, original.Length);
                foreach (int index in subset)
                {
                    temp[index] = pattern[index];
                }

                replacements.Add(new string(temp));
            }

            return replacements;
        }

        private static List<int> GetPatternPositions(string pattern, int maxIndex, char excludeCharacter)
        {
            List<int> positions = new List<int>();

            for (int i = 0; i < maxIndex; i++)
            {
                if (pattern[i] != excludeCharacter)
                    positions.Add(i);
            }

            return positions;
        }
    }

    public static class ArrayUtility
    {
        public static List<T[]> CreateSubsets<T>(T[] originalArray)
        {
            List<T[]> subsets = new List<T[]>();

            for (int i = 0; i < originalArray.Length; i++)
            {
                int subsetCount = subsets.Count;
                subsets.Add(new T[] { originalArray[i] });

                for (int j = 0; j < subsetCount; j++)
                {
                    T[] newSubset = new T[subsets[j].Length + 1];
                    subsets[j].CopyTo(newSubset, 0);
                    newSubset[newSubset.Length - 1] = originalArray[i];
                    subsets.Add(newSubset);
                }
            }

            return subsets;
        }
    }
}