Minimize flipping of bits in given Binary string to make count of 10 equal to 01

Given binary string str, the task is to choose any index and change into 0 or 1, and do this in minimum steps such that the count of substring 01 is equal to 10.

Examples:

Input: str = “01101”
Output: 01100
Explanation: 01 as a substring repeat 2 times in a string, 10 as a substring repeat 1 times in a string. So, change last char 1 into 0 then count of 01 and 10 is 1 and equal

Input: str = “01101010”
Output: 01101010

Approach: If we can observe that if the first and last character of the string is the same so the count of “01” is equal to 1 because by induction is always one character is present in the middle of the string so, we can split a string into two parts s[1….i], [i…n] so AB(s) = BA(s).

• If the first and last characters are not the same, then change the first character to the last character.
• After performing the above steps, print the value of str as the answer.

Below is the implementation of the above approach.

C++

// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;

// Function to make the count equal
string MakeEqual(string str)
{

    // Take first and last char of string
    char FirstChar = str[0];
    char LastChar = str[str.size() - 1];

    // Compare both the char
    if (FirstChar != LastChar) {

        // Copy lastchar inplace of
        // firstchar or viceversa
        str[0] = LastChar;
    }

    // If above condition is not true so
    // string remain unchanged
    // Return string
    return str;
}

// Driver Code
int main()
{

    string str = "0110101";
    string ans = MakeEqual(str);
    cout << ans;
    return 0;
}

Java

// Java program for the above approach
class GFG
{

  // Function to make the count equal
  static String MakeEqual(String str) {

    // Take first and last char of String
    char FirstChar = str.charAt(0);
    char LastChar = str.charAt(str.length() - 1);

    // Compare both the char
    if (FirstChar != LastChar) {

      // Copy lastchar inplace of
      // firstchar or viceversa
      str = str.substring(1, str.length());
      str = LastChar + str;

    }

    // If above condition is not true so
    // String remain unchanged
    // Return String
    return str;
  }

  // Driver Code
  public static void main(String args[]) {

    String str = "0110101";
    String ans = MakeEqual(str);
    System.out.println(ans);
  }
}

// This code is contributed by saurabh_jaiswal.

Python3

# python3 program for the above approach

# Function to make the count equal
def MakeEqual(str):

    # Take first and last char of string
    FirstChar = str[0]
    LastChar = str[-1]

    # Compare both the char
    if (FirstChar != LastChar):

        # Copy lastchar inplace of
        # firstchar or viceversa
        str[0] = LastChar

    # If above condition is not true so
    # string remain unchanged
    # Return string
    return ''.join(str)

# Driver Code
if __name__ == "__main__":

    str = "0110101"
    ans = MakeEqual(list(str))
    print(ans)

    # This code is contributed by rakeshsahni

C#

// C# program for the above approach
using System;

public class GFG
{

  // Function to make the count equal
  static String MakeEqual(String str) {

    // Take first and last char of String
    char FirstChar = str[0];
    char LastChar = str[str.Length - 1];

    // Compare both the char
    if (FirstChar != LastChar) {

      // Copy lastchar inplace of
      // firstchar or viceversa
      str = str.Substring(1, str.Length - 1);
      str = LastChar + str;

    }

    // If above condition is not true so
    // String remain unchanged
    // Return String
    return str;
  }

  // Driver Code
  public static void Main(String []args) {

    String str = "0110101";
    String ans = MakeEqual(str);
    Console.WriteLine(ans);
  }
}

// This code is contributed by shikhasingrajput

Javascript

<script>
    // JavaScript code for the above approach

    // Function to make the count equal
    function MakeEqual(str)
    {

        // Take first and last char of string
        str = str.split('')
        let FirstChar = str[0];
        let LastChar = str[str.length - 1];

        // Compare both the char
        if (FirstChar != LastChar)
        {

            // Copy lastchar inplace of
            // firstchar or viceversa
            str[0] = LastChar;
        }

        // If above condition is not true so
        // string remain unchanged
        // Return string
        return str.join('');
    }

    // Driver Code
    let str = "0110101";
    let ans = MakeEqual(str);
    document.write(ans);

     // This code is contributed by Potta Lokesh
</script>

Output:

1110101

Time Complexity: O(1), The time complexity of this program is O(1) because it only performs constant operations like accessing characters in the string, comparing characters, and assigning new values to the string. Therefore, the time taken by the program will be the same for all input sizes.
Auxiliary Space: O(1), The space complexity of this program is O(1) because it only uses a fixed amount of memory to store the input string, two characters for the first and last characters of the string, and a string variable to store the modified string. Therefore, the space used by the program will remain constant for all input sizes.