Minimum changes required to make first string substring of second string

Given two strings S1 and S2 ( size of S1 <= Size of S2 ). The task is to find the minimum number of characters to be replaced in the string S2, such that the string S1 is a substring of S2.

Examples:

Input : S1 = cdef, S2 = abbdef
Output : 1

Input : S1 = gfg, S2 = fgg
Output : 2


Approach:

  1. Traverse the string S2
    • From every index in S2, check the number of mis-matching characters in substring of length of S1
    • Store and update the minimum of prev and current mis-match in ans
  2. Return ans.

Below is the implementation of the above approach:

C++

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// CPP program to find the minimum number of
// characters to be replaced in string S2, such
// that S1 is a substring of S2
  
#include <bits/stdc++.h>
using namespace std;
  
// Function to find the minimum number of
// characters to be replaced in string S2, such
// that S1 is a substring of S2
int minimumChar(string S1, string S2)
{
    // Get the sizes of both strings
    int n = S1.size(), m = S2.size();
  
    int ans = INT_MAX;
  
    // Traverse the string S2
    for (int i = 0; i < m - n + 1; i++) {
        int minRemovedChar = 0;
  
        // From every index in S2, check the number of
        // mis-matching characters in substring of
        // length of S1
        for (int j = 0; j < n; j++) {
            if (S1[j] != S2[i + j]) {
                minRemovedChar++;
            }
        }
  
        // Take minimum of prev and current mis-match
        ans = min(minRemovedChar, ans);
    }
  
    // return answer
    return ans;
}
  
// Driver Code
int main()
{
    string S1 = "abc";
    string S2 = "paxzk";
  
    cout << minimumChar(S1, S2);
  
    return 0;
}

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Java














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// Java program to find the minimum  


// number of characters to be  


// replaced in string S2, such 


// that S1 is a substring of S2 


import java.io.*; 


  


class GFG  


{ 


  


// Function to find the minimum  


// number of characters to be  


// replaced in string S2, such 


// that S1 is a substring of S2 


static int minimumChar(String S1, 


                       String S2) 


{ 


    // Get the sizes of both strings 


    int n = S1.length(); 


    int m = S2.length(); 


  


    int ans = Integer.MAX_VALUE ; 


  


    // Traverse the string S2 


    for (int i = 0; i < m - n + 1; i++) 


    { 


        int minRemovedChar = 0; 


  


        // From every index in S2, check  


        // the number of mis-matching  


        // characters in substring of 


        // length of S1 


        for (int j = 0; j < n; j++)  


        { 


            if (S1.charAt(j) != S2.charAt(i + j))  


            { 


                minRemovedChar++; 


            } 


        } 


  


        // Take minimum of prev and  


        // current mis-match 


        ans = Math.min(minRemovedChar, ans); 


    } 


  


    // return answer 


    return ans; 


} 


  


// Driver Code 


public static void main (String[] args)  


{ 


    String S1 = "abc"; 


    String S2 = "paxzk"; 


      


    System.out.println(minimumChar(S1, S2)); 


} 


} 


  


// This code is contributed by Shashank 



















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Python3





# Python3 program to find the minimum

# number of characters to be replaced

# in string S2, such that S1 is a

# substring of S2

import sys 


# Function to find the minimum number of

# characters to be replaced in string S2,

# such that S1 is a substring of S2

def minimumChar(S1, S2):


	# Get the sizes of both strings

	n, m = len(S1), len(S2)


	ans = sys.maxsize


	# Traverse the string S2

	for i in range(m – n + 1):

		minRemovedChar = 0


		# From every index in S2, check the

		# number of mis-matching characters

		# in substring of length of S1

		for j in range(n):

			if (S1[j] != S2[i + j]):

				minRemovedChar += 1


		# Take minimum of prev and

		# current mis-match

		ans = min(minRemovedChar, ans)


	# return answer

	return ans


# Driver Code

if __name__ == ‘__main__’:

	S1 = “abc”

	S2 = “paxzk”

	print(minimumChar(S1, S2))


# This code is contributed

# by PrinciRaj1992



C#














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// C# program to find the minimum  


// number of characters to be  


// replaced in string S2, such 


// that S1 is a substring of S2 


using System; 


  


class GFG  


{ 


  


// Function to find the minimum  


// number of characters to be  


// replaced in string S2, such 


// that S1 is a substring of S2 


static int minimumChar(String S1, 


                       String S2) 


{ 


    // Get the sizes of both strings 


    int n = S1.Length; 


    int m = S2.Length; 


  


    int ans = Int32.MaxValue ; 


  


    // Traverse the string S2 


    for (int i = 0; i < m - n + 1; i++) 


    { 


        int minRemovedChar = 0; 


  


        // From every index in S2, check  


        // the number of mis-matching  


        // characters in substring of 


        // length of S1 


        for (int j = 0; j < n; j++)  


        { 


            if (S1[j] != S2[i + j])  


            { 


                minRemovedChar++; 


            } 


        } 


  


        // Take minimum of prev and  


        // current mis-match 


        ans = Math.Min(minRemovedChar, ans); 


    } 


  


    // return answer 


    return ans; 


} 


  


// Driver Code 


public static void Main()  


{ 


    String S1 = "abc"; 


    String S2 = "paxzk"; 


      


    Console.WriteLine(minimumChar(S1, S2)); 


} 


} 


  


// This code is contributed  


// by Akanksha Rai(Abby_akku) 



















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PHP














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<?php 


// PHP program to find the minimum  


// number of characters to be replaced  


// in string S2, such that S1 is a  


// substring of S2  


  


// Function to find the minimum number  


// of characters to be replaced in  


// string S2, such that S1 is a  


// substring of S2  


function minimumChar($S1, $S2)  


{  


    // Get the sizes of both strings  


    $n = strlen($S1); 


    $m = strlen($S2);  


  


    $ans = PHP_INT_MAX;  


  


    // Traverse the string S2  


    for ($i = 0; $i < $m - $n + 1; $i++)  


    {  


        $minRemovedChar = 0;  


  


        // From every index in S2, check  


        // the number of mis-matching  


        // characters in substring of  


        // length of S1  


        for ($j = 0; $j < $n; $j++)  


        {  


            if ($S1[$j] != $S2[$i + $j])  


            {  


                $minRemovedChar++;  


            }  


        }  


  


        // Take minimum of prev and  


        // current mis-match  


        $ans = min($minRemovedChar, $ans);  


    }  


  


    // return answer  


    return $ans;  


}  


  


// Driver Code  


$S1 = "abc";  


$S2 = "paxzk";  


  


echo minimumChar($S1, $S2);  


  


// This code is contributed by ajit. 


?> 



















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Output:


2





Time Complexity: O(N * M).



          
          
          
          

            

    

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