Generate a string which differs by only a single character from all given strings

// C# program to implement
// the above approach
using System;
class GFG{
    
// Function to check if a given string
// differs by a single character from
// all the strings in an array
static bool check(String ans, String[] s,
                  int n, int m)
{
    
    // Traverse over the strings
    for(int i = 1; i < n; ++i)
    {
        
        // Stores the count of characters
        // differing from the strings
        int count = 0;
        for(int j = 0; j < m; ++j)
        {
            if (ans[j] != s[i][j])
                count++;
        }

        // If differs by more than one
        // character
        if (count > 1)
            return false;
    }
    return true;
}

// Function to find the string which only
// differ at one position from the all
// given strings of the array
static String findString(String[] s)
{
    
    // Size of the array
    int n = s.Length;
    String ans = s[0];
    
    // Length of a string
    int m = ans.Length;

    int flag = 0;

    for(int i = 0; i < m; ++i)
    {
        for(int j = 0; j < 26; ++j)
        {
            String x = ans;

            // Replace i-th character by all
            // possible characters
            x = x.Replace(x[i], (char)(j + 'a'));

            // Check if it differs by a
            // single character from all
            // other strings
            if (check(x, s, n, m))
            {
                ans = x;
                flag = 1;
                break;
            }
        }

        // If desired string is obtained
        if (flag == 1)
            break;
    }

    // Print the answer
    if (flag == 0)
        return "-1";
    else
        return ans;
}

// Driver code
public static void Main(String []args)
{
    String []s = { "geeks", "teeds" };

    // Function call
    Console.WriteLine(findString(s));
}
}

// This code is contributed by Rajput-Ji

using System;
using System.Collections.Generic;

class Program {
    // Function to find the string which differs at one
    // position from all given strings
    static string FindString(List<string> s)
    {
        // Size of the array
        int n = s.Count;

        // Length of a string
        int m = s[0].Length;

        // Create a dictionary to store the frequency of
        // each generated string
        Dictionary<string, int> frequencyMap
            = new Dictionary<string, int>();

        // Generate all possible strings that can be formed
        // by changing exactly one character in each input
        // string
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                char[] temp = s[i].ToCharArray();
                for (char ch = 'a'; ch <= 'z'; ch++) {
                    temp[j] = ch;
                    string modifiedString
                        = new string(temp);
                    if (frequencyMap.ContainsKey(
                            modifiedString)) {
                        frequencyMap[modifiedString]++;
                    }
                    else {
                        frequencyMap[modifiedString] = 1;
                    }
                }
            }
        }

        // Traverse the dictionary and find the string that
        // differs from all input strings at exactly one
        // position
        foreach(var kvp in frequencyMap)
        {
            if (kvp.Value == n && !s[0].Equals(kvp.Key)) {
                int count = 0;
                for (int i = 0; i < m; i++) {
                    if (s[0][i] != kvp.Key[i]) {
                        count++;
                    }
                }
                if (count == 1) {
                    return kvp.Key;
                }
            }
        }

        // If no such string is found, return "-1"
        return "-1";
    }

    // Driver code
    static void Main()
    {
        // Input list of strings
        List<string> s
            = new List<string>{ "abac", "zdac", "bdac" };

        // Function call
        Console.WriteLine(FindString(s));
    }
}