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)
Auxiliary Space: O(1)