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Swap all even and odd bits of a number

The given problem requires swapping all even and odd bits of a given number. In binary representation, even bits are the positions with 0-based indexing 0, 2, 4, etc., and odd bits are the positions with 1-based indexing 1, 3, 5, etc. The task is to interchange the values of all even and odd bit positions in the binary representation of the given number.

Problem Statement

The goal is to write an algorithm that takes an integer as input and returns a new integer with all even and odd bits swapped. We will represent the integer in binary form and perform the swapping operation on the binary representation.

Explanation with an Example

Let's take an example to understand the problem better. Consider the input number 42 (in binary 101010). After swapping the even and odd bits, the output should be 21 (in binary 010101).

Binary representation of 42: 1 0 1 0 1 0 After swapping even and odd bits: 0 1 0 1 0 1

Pseudocode

The following pseudocode represents the algorithm for swapping all even and odd bits of a given number:

1. Read the input number n.
    2. Get all the even bits of n using bitwise AND operation with a mask that has 1's at even positions and 0's at odd positions. Shift this result right by 1 to bring it to odd positions.
    3. Get all the odd bits of n using bitwise AND operation with a mask that has 1's at odd positions and 0's at even positions. Shift this result left by 1 to bring it to even positions.
    4. Combine the results obtained in steps 2 and 3 using bitwise OR operation to get the final result.
    5. Display the original number and the resultant number.

Algorithm with Explanation

  1. Start
  2. Read the input number n.
  3. Create a mask for even bits and odd bits:
    • Mask for even bits: 2863311530 (in binary 10101010101010101010101010101010)
    • Mask for odd bits: 1431655765 (in binary 01010101010101010101010101010101)
  4. Calculate the even bits by performing a bitwise AND operation between n and the mask for even bits. Then, right shift the result by 1 to bring it to odd positions. Store this result in the variable even.
  5. Calculate the odd bits by performing a bitwise AND operation between n and the mask for odd bits. Then, left shift the result by 1 to bring it to even positions. Store this result in the variable odd.
  6. Combine the even and odd values obtained in steps 4 and 5 using the bitwise OR operation. Store the result in the variable result.
  7. Display the original number n and the resultant number result.
  8. End

Code Solution

Here given code implementation process.

// C Program 
// Swap all odd and even bits
#include <stdio.h>

// Swap two bits in a given number
void swapEvenOddBits(int n)
{
	// Get all even active bits
	int even = (n & 2863311530) >> 1;
	// Get all Odd active bits
	int odd = (n & 1431655765) << 1;
	int result = even | odd;
	// Display calculated result
	printf(" Number : %d", n);
	printf("\n Output : %d\n\n", result);
}
int main()
{
	// Test cases
	// 010000 => 100000 
	swapEvenOddBits(16);
	// 00100011 (35) =>  00010011 (19)
	swapEvenOddBits(35);
	//  00001111 (15)  => 11110000 (1s) => (11110001) (2s)
	//  1111110001 (-15) => 11110010 (-14) 
	swapEvenOddBits(-15);
	// 1010 (10) => 0101
	swapEvenOddBits(10);
	return 0;
}

Output

 Number : 16
 Output : 32

 Number : 35
 Output : 19

 Number : -15
 Output : -14

 Number : 10
 Output : 5

/*
  Java Program for
  Swap all odd and even bits
*/
public class BitExchange
{
	// Swap two bits in a given number
	public void swapEvenOddBits(int n)
	{
		// Get all even active bits
		long even = (n & 2863311530L) >> 1;
		// Get all Odd active bits
		long odd =  (n & 1431655765) << 1;
		long result = even | odd;
		// Display calculated result
		System.out.print(" Number : " + n);
		System.out.print("\n Output : " + result + "\n\n");
	}
	public static void main(String[] args)
	{
		BitExchange task = new BitExchange();
		//  Test cases
		//  010000 => 100000 (32)
		task.swapEvenOddBits(16);
		//  00100011 (35) =>  00010011 (19)
		task.swapEvenOddBits(35);
		//  00001111 (15)  => 11110000 (1s) => (11110001) (2s)
		//  1111110001 (-15) => 11110010 (-14) 
		task.swapEvenOddBits(-15);
		//  1010 (10) => 0101
		task.swapEvenOddBits(10);
	}
}

Output

 Number : 16
 Output : 32

 Number : 35
 Output : 19

 Number : -15
 Output : -14

 Number : 10
 Output : 5

// Include header file
#include <iostream>
using namespace std;

/*
  C++ Program for
  Swap all odd and even bits
*/

class BitExchange
{
	public:
		// Swap two bits in a given number
		void swapEvenOddBits(int n)
		{
			// Get all even active bits
			int even = (n & 2863311530) >> 1;
			// Get all Odd active bits
			int odd = (n & 1431655765) << 1;
			int result = even | odd;
			// Display calculated result
			cout << " Number : " << n;
			cout << "\n Output : " << result << "\n\n";
		}
};
int main()
{
	BitExchange task = BitExchange();
	//  Test cases
	//  010000 => 100000 (32)
	task.swapEvenOddBits(16);
	//  00100011 (35) =>  00010011 (19)
	task.swapEvenOddBits(35);
	//  00001111 (15)  => 11110000 (1s) => (11110001) (2s)
	//  1111110001 (-15) => 11110010 (-14)
	task.swapEvenOddBits(-15);
	//  1010 (10) => 0101
	task.swapEvenOddBits(10);
	return 0;
}

Output

 Number : 16
 Output : 32

 Number : 35
 Output : 19

 Number : -15
 Output : -14

 Number : 10
 Output : 5

// Include namespace system
using System;
/*
  C# Program for
  Swap all odd and even bits
*/
public class BitExchange
{
	// Swap two bits in a given number
	public void swapEvenOddBits(int n)
	{
		// Get all even active bits
		long even = (n & 2863311530) >> 1;
		// Get all Odd active bits
		long odd = (n & 1431655765) << 1;
		long result = even | odd;
		// Display calculated result
		Console.Write(" Number : " + n);
		Console.Write("\n Output : " + result + "\n\n");
	}
	public static void Main(String[] args)
	{
		BitExchange task = new BitExchange();
		//  Test cases
		//  010000 => 100000 (32)
		task.swapEvenOddBits(16);
		//  00100011 (35) =>  00010011 (19)
		task.swapEvenOddBits(35);
		//  00001111 (15)  => 11110000 (1s) => (11110001) (2s)
		//  1111110001 (-15) => 11110010 (-14)
		task.swapEvenOddBits(-15);
		//  1010 (10) => 0101
		task.swapEvenOddBits(10);
	}
}

Output

 Number : 16
 Output : 32

 Number : 35
 Output : 19

 Number : -15
 Output : -14

 Number : 10
 Output : 5

<?php
/*
  Php Program for
  Swap all odd and even bits
*/
class BitExchange
{
	// Swap two bits in a given number
	public	function swapEvenOddBits($n)
	{
		// Get all even active bits
		$even = ($n & 2863311530) >> 1;
		// Get all Odd active bits
		$odd =  ($n & 1431655765) << 1;
		$result = $even | $odd;
		// Display calculated result
		echo " Number : ". $n;
		echo "\n Output : ". $result ."\n\n";
	}
}

function main()
{
	$task = new BitExchange();
	//  Test cases
	//  010000 => 100000 (32)
	$task->swapEvenOddBits(16);
	//  00100011 (35) =>  00010011 (19)
	$task->swapEvenOddBits(35);
	//  1010 (10) => 0101
	$task->swapEvenOddBits(10);
}
main();

Output

 Number : 16
 Output : 32

 Number : 35
 Output : 19

 Number : 10
 Output : 5

/*
  Node Js Program for
  Swap all odd and even bits
*/
class BitExchange
{
	// Swap two bits in a given number
	swapEvenOddBits(n)
	{
		// Get all even active bits
		var even = (n & 2863311530) >> 1;
		// Get all Odd active bits
		var odd = (n & 1431655765) << 1;
		var result = even | odd;
		// Display calculated result
		process.stdout.write(" Number : " + n);
		process.stdout.write("\n Output : " + result + "\n\n");
	}
}

function main()
{
	var task = new BitExchange();
	//  Test cases
	//  010000 => 100000 (32)
	task.swapEvenOddBits(16);
	//  00100011 (35) =>  00010011 (19)
	task.swapEvenOddBits(35);
	//  00001111 (15)  => 11110000 (1s) => (11110001) (2s)
	//  1111110001 (-15) => 11110010 (-14)
	task.swapEvenOddBits(-15);
	//  1010 (10) => 0101
	task.swapEvenOddBits(10);
}
main();

Output

 Number : 16
 Output : 32

 Number : 35
 Output : 19

 Number : -15
 Output : -14

 Number : 10
 Output : 5

#   Python 3 Program for
#   Swap all odd and even bits

class BitExchange :
	#  Swap two bits in a given number
	def swapEvenOddBits(self, n) :
		#  Get all even active bits
		even = (n & 2863311530) >> 1
		#  Get all Odd active bits
		odd = (n & 1431655765) << 1
		result = even | odd
		#  Display calculated result
		print(" Number : ", n, end = "")
		print("\n Output : ", result ,"\n")
	

def main() :
	task = BitExchange()
	#   Test cases
	#   010000 => 100000 (32)
	task.swapEvenOddBits(16)
	#   00100011 (35) =>  00010011 (19)
	task.swapEvenOddBits(35)
	#   1010 (10) => 0101
	task.swapEvenOddBits(10)

if __name__ == "__main__": main()

Output

 Number :  16
 Output :  32

 Number :  35
 Output :  19

 Number :  10
 Output :  5

#   Ruby Program for
#   Swap all odd and even bits

class BitExchange 
	#  Swap two bits in a given number
	def swapEvenOddBits(n) 
		#  Get all even active bits
		even = (n & 2863311530) >> 1
		#  Get all Odd active bits
		odd = (n & 1431655765) << 1
		result = even | odd
		#  Display calculated result
		print(" Number : ", n)
		print("\n Output : ", result ,"\n\n")
	end

end

def main() 
	task = BitExchange.new()
	#   Test cases
	#   010000 => 100000 (32)
	task.swapEvenOddBits(16)
	#   00100011 (35) =>  00010011 (19)
	task.swapEvenOddBits(35)
	#   1010 (10) => 0101
	task.swapEvenOddBits(10)
end

main()

Output

 Number : 16
 Output : 32

 Number : 35
 Output : 19

 Number : 10
 Output : 5


/*
  Scala Program for
  Swap all odd and even bits
*/
class BitExchange
{
	// Swap two bits in a given number
	def swapEvenOddBits(n: Int): Unit = {
		// Get all even active bits
		var even: Long = (n & 2863311530L) >> 1;
		// Get all Odd active bits
		var odd: Long = (n & 1431655765) << 1;
		var result: Long = even | odd;
		// Display calculated result
		print(" Number : " + n);
		print("\n Output : " + result + "\n\n");
	}
}
object Main
{
	def main(args: Array[String]): Unit = {
		var task: BitExchange = new BitExchange();
		//  Test cases
		//  010000 => 100000 (32)
		task.swapEvenOddBits(16);
		//  00100011 (35) =>  00010011 (19)
		task.swapEvenOddBits(35);
		//  00001111 (15)  => 11110000 (1s) => (11110001) (2s)
		//  1111110001 (-15) => 11110010 (-14)
		task.swapEvenOddBits(-15);
		//  1010 (10) => 0101
		task.swapEvenOddBits(10);
	}
}

Output

 Number : 16
 Output : 32

 Number : 35
 Output : 19

 Number : -15
 Output : -14

 Number : 10
 Output : 5

/*
  Swift 4 Program for
  Swap all odd and even bits
*/
class BitExchange
{
	// Swap two bits in a given number
	func swapEvenOddBits(_ n: Int)
	{
		// Get all even active bits
		let even: Int = (n & 2863311530) >> 1;
		// Get all Odd active bits
		let odd: Int = (n & 1431655765) << 1;
		let result: Int = even | odd;
		// Display calculated result
		print(" Number : ", n, terminator: "");
		print("\n Output : ", result ,"\n");
	}
}
func main()
{
	let task: BitExchange = BitExchange();
	//  Test cases
	//  010000 => 100000 (32)
	task.swapEvenOddBits(16);
	//  00100011 (35) =>  00010011 (19)
	task.swapEvenOddBits(35);
	//  1010 (10) => 0101
	task.swapEvenOddBits(10);
}
main();

Output

 Number :  16
 Output :  32

 Number :  35
 Output :  19

 Number :  10
 Output :  5

/*
  Kotlin Program for
  Swap all odd and even bits
*/
class BitExchange
{
	// Swap two bits in a given number
	fun swapEvenOddBits(n: Long): Unit
	{
		// Get all even active bits
		var even: Long = (n and 2863311530) shr 1;
		// Get all Odd active bits
		var odd: Long = (n and 1431655765) shl 1;
		var result: Long = even or odd;
		// Display calculated result
		print(" Number : " + n);
		print("\n Output : " + result + "\n\n");
	}
}
fun main(args: Array <String> ): Unit
{
	var task: BitExchange = BitExchange();
	//  Test cases
	//  010000 => 100000 (32)
	task.swapEvenOddBits(16);
	//  00100011 (35) =>  00010011 (19)
	task.swapEvenOddBits(35);
	//  1010 (10) => 0101
	task.swapEvenOddBits(10);
}

Output

 Number : 16
 Output : 32

 Number : 35
 Output : 19

 Number : 10
 Output : 5

Output Explanation

Now, let's apply the algorithm to the provided test cases and explain the output:

  1. Test case: swapEvenOddBits(16)

    • Input: 16 (in binary 10000)
    • Even bits: 00000 (right shift of 00000, which remains unchanged)
    • Odd bits: 00000 (left shift of 00000, which remains unchanged)
    • Result: 00000 (00000 OR 00000 = 00000)
    • Output: Original Number: 16, Result: 0

  2. Test case: swapEvenOddBits(35)

    • Input: 35 (in binary 100011)
    • Even bits: 00001 (right shift of 0010)
    • Odd bits: 10000 (left shift of 0100)
    • Result: 10001 (00001 OR 10000 = 10001)
    • Output: Original Number: 35, Result: 17

  3. Test case: swapEvenOddBits(-15)

    • Input: -15 (in binary 11111111111111111111111111110001)
    • Even bits: 1111111111111111111111111111000 (right shift of 1111111111111111111111111111000)
    • Odd bits: 11111111111111111111111111110010 (left shift of 11111111111111111111111111110010)
    • Result: 11111111111111111111111111111010 (1111111111111111111111111111000 OR 11111111111111111111111111110010 = 11111111111111111111111111111010)
    • Output: Original Number: -15, Result: -10

  4. Test case: swapEvenOddBits(10)

    • Input: 10 (in binary 1010)
    • Even bits: 0010 (right shift of 0010)
    • Odd bits: 0101 (left shift of 0101)
    • Result: 0111 (0010 OR 0101 = 0111)
    • Output: Original Number: 10, Result: 7

Time Complexity of the Code

The time complexity of the code is O(1) because it involves a fixed number of bitwise operations, and the number of bits in the input does not affect the complexity. Thus, the code runs in constant time, regardless of the input size.

Finally

In this article, we explored the problem of swapping all even and odd bits of a given number. We discussed the problem statement, provided an explanation with a suitable example, and presented the pseudocode and algorithm to solve the problem. Furthermore, we explained the resultant output for each test case and analyzed the time complexity of the code. By swapping the even and odd bits using bitwise operations, we can efficiently solve this problem for any given integer.

Last updated on by Kalkicode




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