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

Given an array of strings str[] of length N, consisting of strings of the same length, the task is to find the string which only differs by a single character from all the given strings. If no such string can be generated, print -1. In case of multiple possible answers, print any of them.

Example:

Input: str[] = { “abac”, “zdac”, “bdac”}
Output: adac
Explanation:
The string “adac” differs from all the given strings by a single character.

Input: str[] = { “geeks”, “teeds”}
Output: teeks

Approach: Follow the steps below to solve the problem:

Set the first string as the answer.
Now, replace the first character of the string to all possible characters and check if it differs by a single character from the other strings or not.
Repeat this process for all the characters in the first string.
If any such string of the required type is found from the above step, print the string.
If no such situation arises where replacing a single character of the first string generates a string of the required type, print -1.

Below is the implementation of the above approach.

C++

// C++ Program to implement
// the above approach
#include <bits/stdc++.h>
#define ll long long
 
using namespace std;
 
// Function to check if a given string
// differs by a single character from
// all the strings in an array
bool check(string ans, vector<string>& s,
           int n, int m)
{
 
    // Traverse over the srings
    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
string findString(vector<string>& s)
{
 
    // Size of the array
    int n = s.size();
 
    // Length of a string
    int m = s[0].size();
 
    string ans = s[0];
 
    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[i] = (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
int main()
{
 
    vector<string> s = { "geeks", "teeds" };
 
    // Function call
    cout << findString(s) << endl;
}

Java

// Java program to implement
// the above approach
import java.util.*;
 
class GFG{
     
// Function to check if a given string
// differs by a single character from
// all the strings in an array
static boolean check(String ans, String[] s,
                     int n, int m)
{
     
    // Traverse over the srings
    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.charAt(j) != s[i].charAt(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.charAt(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
    System.out.println(findString(s));
}
}
 
// This code is contributed by chitranayal

Python3

# Python3 program to implement
# the above approach
 
# Function to check if a given string 
# differs by a single character from
# all the strings in an array
def check(ans, s, n, m):
 
    # Traverse over the srings
    for i in range(1, n):
 
        # Stores the count of characters
        # differing from the strings
        count = 0
        for j in range(m):
            if(ans[j] != s[i][j]):
                count += 1
 
        # 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
def findString(s):
 
    # Size of the array
    n = len(s)
 
    # Length of a string
    m = len(s[0])
 
    ans = s[0]
    flag = 0
 
    for i in range(m):
        for j in range(26):
            x = list(ans)
 
            # Replace i-th character by all
            # possible characters
            x[i] = chr(j + ord('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 ''.join(ans)
 
# Driver Code
 
# Given array of strings
s = [ "geeks", "teeds" ]
 
# Function call
print(findString(s))
 
# This code is contributed by Shivam Singh

C#

// 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 srings
    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

Output:

teeks

Time Complexity: O(N * M² * 26)
Auxiliary Space: O(M)

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My Personal Notes

C++

Java

Python3

C#

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