Minimum number of steps needed to remove the substring K from given string

• Difficulty Level : Medium
• Last Updated : 01 Jun, 2021

Given a binary string S, and a substring K, the task is to find the minimum no of steps required to flip the characters in a binary string such that it doesn’t contain the given substring K. Note: In one step we can change 0 to 1 or vice versa.
Examples:

Input: S = “0111011”, K = “011”
Output:
Explanation:
In the above string we have the substring 011 for 2 times, hence change the 3rd bit and 7th bit.

Input: S = “010010”, K = “0100”
Output:
Explanation:
In the above string we have the substring 0100 for 1 time, change the 4th bit of the string to 1.

Naive Approach: The naive approach is to use the Pattern Searching. Iterate through the string for N! times(N = length of the binary string). In every iteration check for the substring K and if its a match then increment the count. At last, print the count which will be the number of steps required to make the string such that it doesn’t contain the given substring K.

Time Complexity: O(M*N) where M is the length of substring and N is the length of the binary string.
Auxiliary Space: O(1)

Efficient Approach: To optimize the above method, the idea is to replace the substring with an empty string and subtract the resultant string length from original string length. After this divide the resultant string with the length of the given substring K to get the minimum no of steps required to flip the characters of the given string S so that it doesn’t contain the given substring K.

Below is the implementation of the above approach:

C++

 // C++ program for the above approach#include#include using namespace std; // Function that counts the total// number of character to be flipped// such the string b doesn't contains// string sub as a substringint flipCharacters(string b,                   string sub){         // Replacing the substring with ""    // and find the difference between    // the length of the resultant    // string and the original    // string length    int res = b.size();    boost::replace_all(b, sub, "");    res = res - b.size();                  // Divide the result    // with substring length    int temp = res / sub.size();     // Return the final count    return temp;} // Driver Codeint main(){         // Given string S and substring K    string S = "010010";    string K = "0100";     // Function call    int result = flipCharacters(S, K);     // Print the minimum flip    cout << (result);} // This code is contributed by Amit Katiyar

Java

 // Java program for the above approachimport java.util.*; public class Test {     // Function that counts the total    // number of character to be flipped    // such the string b doesn't contains    // string sub as a substring    static int flipCharacters(String b,                              String sub)    {         // Replacing the substring with ""        // and find the difference between        // the length of the resultant        // string and the original        // string length         int res = b.length()                  - b.replaceAll(sub, "")                        .length();         // Divide the result        // with substring length         int temp = res / sub.length();         // Return the final count        return temp;    }     // Driver Code    public static void main(String[] args)    {         // Given string S and substring K        String S = "010010";        String K = "0100";         // Function Call        int result = flipCharacters(S, K);         // Print the minimum flip        System.out.println(result);    }}

Python3

 # Python3 program for the above approachdef flipCharacters(b, sub):         # Replace the substring with    # "" (emptryString)    b1 = b.replace(sub, "")         n = int((len(b)-len(b1))/len(sub))         return n # Driver Codeif __name__ == '__main__': # Given string S and substring K    S ="010010"    X ="0100" # Function Call    result = flipCharacters(S, X) # Print the minimum flip    print(result)

C#

 // C# program for the above approachusing System;class GFG{    // Function that counts the total  // number of character to be flipped  // such the string b doesn't contains  // string sub as a substring  static int flipCharacters(string b,                            string sub)  {     // Replacing the substring with ""    // and find the difference between    // the length of the resultant    // string and the original    // string length     int res = b.Length -              b.Replace(sub, "").Length;     // Divide the result    // with substring length    int temp = res / sub.Length;     // Return the final count    return temp;  }   // Driver Code  public static void Main(string[] args)  {     // Given string S and substring K    string S = "010010";    string K = "0100";     // Function Call    int result = flipCharacters(S, K);     // Print the minimum flip    Console.Write(result);  }} // This code is contributed by rutvik_56

Javascript


Output:
1

Time Complexity: O(N), where N is the length of the string.
Auxiliary Space: O(1)

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