Find the last player to be able to flip a character in a Binary String


Welcome to our comprehensive guide on a stimulating algorithmic problem involving binary strings. We will be examining a problem where we need to find the last player who can flip a character in a binary string. This problem is a great exercise for understanding game theory and binary string manipulation.

Problem Statement

Given a binary string, we have two players who take turns to flip a '1' into a '0'. The player who cannot make a move loses the game. The task is to find out who, between Player 1 and Player 2, will be the last player to be able to flip a character.

Approach

We will iterate over the binary string, counting the number of '1's. If the number of '1's is even, Player 2 will be the last to flip a '1', as Player 1 always starts the game. If the number of '1's is odd, Player 1 will be the last to flip a '1'.

Implementation

Example

Here're the programs to the above algorithm −

#include <stdio.h>
#include <string.h>

// Function to determine the last player to flip a character
char* lastPlayer(char* s) {
   int count = 0;
   for (int i = 0; i < strlen(s); i++) {
      if (s[i] == '1')
         count++;
      }
   return (count % 2 == 0) ? "Player 2" : "Player 1";
}

int main() {
   char s[] = "1101";
    
   printf("The last player to be able to flip a character is: %s\n", lastPlayer(s));
   return 0;
}

Output

The last player to be able to flip a character is: Player 1
#include<bits/stdc++.h>
using namespace std;

string lastPlayer(string s) {
   int count = 0;
   for (char c : s) {
      if (c == '1')
         count++;
      }
   return (count % 2 == 0) ? "Player 2" : "Player 1";
}

int main() {
   string s="1101";
   
   cout << "The last player to be able to flip a character is: " << lastPlayer(s) << endl;
   return 0;
}

Output

The last player to be able to flip a character is: Player 1
public class Main {
   // Function to determine the last player to flip a character
   public static String lastPlayer(String s) {
      int count = 0;
      for (char c : s.toCharArray()) {
         if (c == '1')
            count++;
      }
      return (count % 2 == 0) ? "Player 2" : "Player 1";
   }

   public static void main(String[] args) {
      String s = "1101";
        
      System.out.println("The last player to be able to flip a character is: " + lastPlayer(s));
   }
}

Output

The last player to be able to flip a character is: Player 1
def last_player(s):
   count = s.count('1')
   return "Player 2" if count % 2 == 0 else "Player 1"

def main():
   s = "1101"
   print("The last player to be able to flip a character is:", last_player(s))

if __name__ == "__main__":
   main()

Output

The last player to be able to flip a character is: Player 1

This program inputs a binary string and outputs the last player who can flip a character.

Test Case Example

Let's consider an example to clarify this problem and its solution −

Suppose the binary string is "1101".

  • We start by counting the number of '1's in the binary string.

  • The count of '1's in "1101" is 3, which is an odd number.

  • Since the count is odd, Player 1 will be the last to flip a '1'.

  • Therefore, the output will be "The last player to be able to flip a character is: Player 1".

Conclusion

In this guide, we've learned how to determine the last player who can flip a character in a binary string. This problem is an interesting exploration of game theory and binary string manipulation.

Updated on: 20-Oct-2023

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