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Code Bit Logic

Swap two nibbles in a byte

In this problem, we are given a byte (8 bits) and we need to swap its two nibbles. A nibble is a group of 4 bits. The goal is to interchange the positions of the first four bits with the last four bits.

Problem Statement:

Given an 8-bit number (byte), we need to swap its two nibbles and obtain the result.

Example:

Let's take the byte 175 (binary: 10101111) as an example. The first nibble is 1010 and the second nibble is 1111. We need to swap them to get 11111010, which is the result 250.

 (175)   10101111
 4 (bit) 1010 1111
            ↘ ↙
         1111 1010
 Result  (11111010) (250)

Pseudocode

swapNibbles(num):
    // Get the first nibble (lower 4 bits)
    firstNibble = num & 15   // 15 in binary: 00001111
    
    // Get the second nibble (upper 4 bits)
    secondNibble = (num & 240) >> 4  // 240 in binary: 11110000
    
    // Swap the nibbles by combining them in reverse order
    result = (firstNibble << 4) | secondNibble
    
    return result

Algorithm Explanation

  1. Create a function swapNibbles(num) that takes an integer num as input and returns an integer as output.
  2. To get the first nibble, perform a bitwise AND operation between num and 15. This can be done by using the binary mask 00001111, where the lower 4 bits are set to 1 and the upper 4 bits are set to 0. This will extract the lower 4 bits of the number as the first nibble.
  3. To get the second nibble, perform a bitwise AND operation between num and 240 and then shift the result 4 positions to the right. The binary mask 11110000 extracts the upper 4 bits of the number, and shifting it 4 positions to the right gives us the second nibble.
  4. Now, we have the first nibble and the second nibble. To swap them, we shift the first nibble 4 positions to the left (firstNibble << 4) and then combine it with the second nibble using the bitwise OR operation (|). This gives us the final result with the nibbles swapped.
  5. Return the result.

Code Solution

Here given code implementation process.

// C program 
// Swap two nibbles in a byte
#include <stdio.h>

void swapNibbles(int num)
{
    // (  num & 15 ) Get initial 4 bit set bits in number
    // (( num & 15) << 4) this is moving initial 4 bits in left side [A]
    // (( num & 240)) Get next 4 bit set bits in number
    // (( num & 240) >> 4 ) moving next 4 bits in right side [B]
    // A or B return swap version of 4 bits
    int result = ((num & 15) << 4) | ((num & 240) >> 4 ); 

    printf("\n Number : %d",num);
    printf("\n Result : %d",result);
}
int main(int argc, char const *argv[])
{
    
    // (175)   10101111
    // 4 (bit) 1010 1111
    //            ↘ ↙
    //         1111 1010
    // Result  (11111010) (250)
    swapNibbles(175);
    // (225)   11100001
    // 4 (bit) 1110 0001
    //            ↘ ↙
    //         0001 1110
    // Result  (00011110) (30)
    swapNibbles(225);
    // (2)     00000010
    // 4 (bit) 0000 0010
    //            ↘ ↙
    //         0010 0000
    // Result  (00100000) (32)
    swapNibbles(2);

    return 0;
}

Output

 Number : 175
 Result : 250
 Number : 225
 Result : 30
 Number : 2
 Result : 32
/*
  Java program
  Swap two nibbles in a byte 
*/
public class BitSwap
{
	// Interchange 4 bits of a number
	public void swapNibbles(int num)
	{
		// (  num & 15 ) Get initial 4 bit set bits in number
		// (( num & 15) << 4) this is moving initial 4 bits in left side [A]
		// (( num & 240)) Get next 4 bit set bits in number
		// (( num & 240) >> 4 ) moving next 4 bits in right side [B]
		// A or B return swap version of 4 bits
		int result = ((num & 15) << 4) | ((num & 240) >> 4);
		System.out.print("\n Number : " + num);
		System.out.print("\n Result : " + result);
	}
	public static void main(String[] args)
	{
		BitSwap task = new BitSwap();
		// (175)   10101111
		// 4 (bit) 1010 1111
		//            ↘ ↙
		//         1111 1010
		// Result  (11111010) (250)
		task.swapNibbles(175);
		// (225)   11100001
		// 4 (bit) 1110 0001
		//            ↘ ↙
		//         0001 1110
		// Result  (00011110) (30)
		task.swapNibbles(225);
		// (2)     00000010
		// 4 (bit) 0000 0010
		//            ↘ ↙
		//         0010 0000
		// Result  (00100000) (32)
		task.swapNibbles(2);
	}
}

Output

 Number : 175
 Result : 250
 Number : 225
 Result : 30
 Number : 2
 Result : 32
// Include header file
#include <iostream>
using namespace std;
/*
  C++ program
  Swap two nibbles in a byte 
*/
class BitSwap
{
	public:
		// Interchange 4 bits of a number
		void swapNibbles(int num)
		{
			// (  num &15 ) Get initial 4 bit set bits in number
			// (( num &15) << 4) this is moving initial 4 bits in left side [A]
			// (( num &240)) Get next 4 bit set bits in number
			// (( num &240) >> 4 ) moving next 4 bits in right side [B]
			// A or B return swap version of 4 bits
			int result = ((num &15) << 4) | ((num &240) >> 4);
			cout << "\n Number : " << num;
			cout << "\n Result : " << result;
		}
};
int main()
{
	BitSwap task = BitSwap();
	// (175)   10101111
	// 4 (bit) 1010 1111
	//            ↘ ↙
	//         1111 1010
	// Result  (11111010) (250)
	task.swapNibbles(175);
	// (225)   11100001
	// 4 (bit) 1110 0001
	//            ↘ ↙
	//         0001 1110
	// Result  (00011110) (30)
	task.swapNibbles(225);
	// (2)     00000010
	// 4 (bit) 0000 0010
	//            ↘ ↙
	//         0010 0000
	// Result  (00100000) (32)
	task.swapNibbles(2);
	return 0;
}

Output

 Number : 175
 Result : 250
 Number : 225
 Result : 30
 Number : 2
 Result : 32
// Include namespace system
using System;
/*
  C# program
  Swap two nibbles in a byte 
*/
public class BitSwap
{
	// Interchange 4 bits of a number
	public void swapNibbles(int num)
	{
		// (  num & 15 ) Get initial 4 bit set bits in number
		// (( num & 15) << 4) this is moving initial 4 bits in left side [A]
		// (( num & 240)) Get next 4 bit set bits in number
		// (( num & 240) >> 4 ) moving next 4 bits in right side [B]
		// A or B return swap version of 4 bits
		int result = ((num & 15) << 4) | ((num & 240) >> 4);
		Console.Write("\n Number : " + num);
		Console.Write("\n Result : " + result);
	}
	public static void Main(String[] args)
	{
		BitSwap task = new BitSwap();
		// (175)   10101111
		// 4 (bit) 1010 1111
		//            ↘ ↙
		//         1111 1010
		// Result  (11111010) (250)
		task.swapNibbles(175);
		// (225)   11100001
		// 4 (bit) 1110 0001
		//            ↘ ↙
		//         0001 1110
		// Result  (00011110) (30)
		task.swapNibbles(225);
		// (2)     00000010
		// 4 (bit) 0000 0010
		//            ↘ ↙
		//         0010 0000
		// Result  (00100000) (32)
		task.swapNibbles(2);
	}
}

Output

 Number : 175
 Result : 250
 Number : 225
 Result : 30
 Number : 2
 Result : 32
<?php
/*
  Php program
  Swap two nibbles in a byte 
*/
class BitSwap
{
	// Interchange 4 bits of a number
	public	function swapNibbles($num)
	{
		// (  num & 15 ) Get initial 4 bit set bits in number
		// (( num & 15) << 4) this is moving initial 4 bits in left side [A]
		// (( num & 240)) Get next 4 bit set bits in number
		// (( num & 240) >> 4 ) moving next 4 bits in right side [B]
		// A or B return swap version of 4 bits
		$result = (($num & 15) << 4) | (($num & 240) >> 4);
		echo "\n Number : ". $num;
		echo "\n Result : ". $result;
	}
}

function main()
{
	$task = new BitSwap();
	// (175)   10101111
	// 4 (bit) 1010 1111
	//            ↘ ↙
	//         1111 1010
	// Result  (11111010) (250)
	$task->swapNibbles(175);
	// (225)   11100001
	// 4 (bit) 1110 0001
	//            ↘ ↙
	//         0001 1110
	// Result  (00011110) (30)
	$task->swapNibbles(225);
	// (2)     00000010
	// 4 (bit) 0000 0010
	//            ↘ ↙
	//         0010 0000
	// Result  (00100000) (32)
	$task->swapNibbles(2);
}
main();

Output

 Number : 175
 Result : 250
 Number : 225
 Result : 30
 Number : 2
 Result : 32
/*
  Node Js program
  Swap two nibbles in a byte 
*/
class BitSwap
{
	// Interchange 4 bits of a number
	swapNibbles(num)
	{
		// (  num & 15 ) Get initial 4 bit set bits in number
		// (( num & 15) << 4) this is moving initial 4 bits in left side [A]
		// (( num & 240)) Get next 4 bit set bits in number
		// (( num & 240) >> 4 ) moving next 4 bits in right side [B]
		// A or B return swap version of 4 bits
		var result = ((num & 15) << 4) | ((num & 240) >> 4);
		process.stdout.write("\n Number : " + num);
		process.stdout.write("\n Result : " + result);
	}
}

function main()
{
	var task = new BitSwap();
	// (175)   10101111
	// 4 (bit) 1010 1111
	//            ↘ ↙
	//         1111 1010
	// Result  (11111010) (250)
	task.swapNibbles(175);
	// (225)   11100001
	// 4 (bit) 1110 0001
	//            ↘ ↙
	//         0001 1110
	// Result  (00011110) (30)
	task.swapNibbles(225);
	// (2)     00000010
	// 4 (bit) 0000 0010
	//            ↘ ↙
	//         0010 0000
	// Result  (00100000) (32)
	task.swapNibbles(2);
}
main();

Output

 Number : 175
 Result : 250
 Number : 225
 Result : 30
 Number : 2
 Result : 32
#   Python 3 program
#   Swap two nibbles in a byte 

class BitSwap :
	#  Interchange 4 bits of a number
	def swapNibbles(self, num) :
		#  (  num & 15 ) Get initial 4 bit set bits in number
		#  (( num & 15) << 4) this is moving initial 4 bits in left side [A]
		#  (( num & 240)) Get next 4 bit set bits in number
		#  (( num & 240) >> 4 ) moving next 4 bits in right side [B]
		#  A or B return swap version of 4 bits
		result = ((num & 15) << 4) | ((num & 240) >> 4)
		print("\n Number : ", num, end = "")
		print("\n Result : ", result, end = "")
	

def main() :
	task = BitSwap()
	#  (175)   10101111
	#  4 (bit) 1010 1111
	#             ↘ ↙
	#          1111 1010
	#  Result  (11111010) (250)
	task.swapNibbles(175)
	#  (225)   11100001
	#  4 (bit) 1110 0001
	#             ↘ ↙
	#          0001 1110
	#  Result  (00011110) (30)
	task.swapNibbles(225)
	#  (2)     00000010
	#  4 (bit) 0000 0010
	#             ↘ ↙
	#          0010 0000
	#  Result  (00100000) (32)
	task.swapNibbles(2)

if __name__ == "__main__": main()

Output

 Number :  175
 Result :  250
 Number :  225
 Result :  30
 Number :  2
 Result :  32
#   Ruby program
#   Swap two nibbles in a byte 

class BitSwap 
	#  Interchange 4 bits of a number
	def swapNibbles(num) 
		#  (  num & 15 ) Get initial 4 bit set bits in number
		#  (( num & 15) << 4) this is moving initial 4 bits in left side [A]
		#  (( num & 240)) Get next 4 bit set bits in number
		#  (( num & 240) >> 4 ) moving next 4 bits in right side [B]
		#  A or B return swap version of 4 bits
		result = ((num & 15) << 4) | ((num & 240) >> 4)
		print("\n Number : ", num)
		print("\n Result : ", result)
	end

end

def main() 
	task = BitSwap.new()
	#  (175)   10101111
	#  4 (bit) 1010 1111
	#             ↘ ↙
	#          1111 1010
	#  Result  (11111010) (250)
	task.swapNibbles(175)
	#  (225)   11100001
	#  4 (bit) 1110 0001
	#             ↘ ↙
	#          0001 1110
	#  Result  (00011110) (30)
	task.swapNibbles(225)
	#  (2)     00000010
	#  4 (bit) 0000 0010
	#             ↘ ↙
	#          0010 0000
	#  Result  (00100000) (32)
	task.swapNibbles(2)
end

main()

Output

 Number : 175
 Result : 250
 Number : 225
 Result : 30
 Number : 2
 Result : 32
/*
  Scala program
  Swap two nibbles in a byte 
*/
class BitSwap
{
	// Interchange 4 bits of a number
	def swapNibbles(num: Int): Unit = {
		// (  num & 15 ) Get initial 4 bit set bits in number
		// (( num & 15) << 4) this is moving initial 4 bits in left side [A]
		// (( num & 240)) Get next 4 bit set bits in number
		// (( num & 240) >> 4 ) moving next 4 bits in right side [B]
		// A or B return swap version of 4 bits
		var result: Int = ((num & 15) << 4) | ((num & 240) >> 4);
		print("\n Number : " + num);
		print("\n Result : " + result);
	}
}
object Main
{
	def main(args: Array[String]): Unit = {
		var task: BitSwap = new BitSwap();
		// (175)   10101111
		// 4 (bit) 1010 1111
		//            ↘ ↙
		//         1111 1010
		// Result  (11111010) (250)
		task.swapNibbles(175);
		// (225)   11100001
		// 4 (bit) 1110 0001
		//            ↘ ↙
		//         0001 1110
		// Result  (00011110) (30)
		task.swapNibbles(225);
		// (2)     00000010
		// 4 (bit) 0000 0010
		//            ↘ ↙
		//         0010 0000
		// Result  (00100000) (32)
		task.swapNibbles(2);
	}
}

Output

 Number : 175
 Result : 250
 Number : 225
 Result : 30
 Number : 2
 Result : 32
/*
  Swift 4 program
  Swap two nibbles in a byte 
*/
class BitSwap
{
	// Interchange 4 bits of a number
	func swapNibbles(_ num: Int)
	{
		// (  num & 15 ) Get initial 4 bit set bits in number
		// (( num & 15) << 4) this is moving initial 4 bits in left side [A]
		// (( num & 240)) Get next 4 bit set bits in number
		// (( num & 240) >> 4 ) moving next 4 bits in right side [B]
		// A or B return swap version of 4 bits
		let result: Int = ((num & 15) << 4) | ((num & 240) >> 4);
		print("\n Number : ", num, terminator: "");
		print("\n Result : ", result, terminator: "");
	}
}
func main()
{
	let task: BitSwap = BitSwap();
	// (175)   10101111
	// 4 (bit) 1010 1111
	//            ↘ ↙
	//         1111 1010
	// Result  (11111010) (250)
	task.swapNibbles(175);
	// (225)   11100001
	// 4 (bit) 1110 0001
	//            ↘ ↙
	//         0001 1110
	// Result  (00011110) (30)
	task.swapNibbles(225);
	// (2)     00000010
	// 4 (bit) 0000 0010
	//            ↘ ↙
	//         0010 0000
	// Result  (00100000) (32)
	task.swapNibbles(2);
}
main();

Output

 Number :  175
 Result :  250
 Number :  225
 Result :  30
 Number :  2
 Result :  32
/*
  Kotlin program
  Swap two nibbles in a byte 
*/
class BitSwap
{
	// Interchange 4 bits of a number
	fun swapNibbles(num: Int): Unit
	{
		// (  num & 15 ) Get initial 4 bit set bits in number
		// (( num & 15) << 4) this is moving initial 4 bits in left side [A]
		// (( num & 240)) Get next 4 bit set bits in number
		// (( num & 240) >> 4 ) moving next 4 bits in right side [B]
		// A or B return swap version of 4 bits
		var result: Int = ((num and 15) shl 4) or((num and 240) shr 4);
		print("\n Number : " + num);
		print("\n Result : " + result);
	}
}
fun main(args: Array < String > ): Unit
{
	var task: BitSwap = BitSwap();
	// (175)   10101111
	// 4 (bit) 1010 1111
	//            ↘ ↙
	//         1111 1010
	// Result  (11111010) (250)
	task.swapNibbles(175);
	// (225)   11100001
	// 4 (bit) 1110 0001
	//            ↘ ↙
	//         0001 1110
	// Result  (00011110) (30)
	task.swapNibbles(225);
	// (2)     00000010
	// 4 (bit) 0000 0010
	//            ↘ ↙
	//         0010 0000
	// Result  (00100000) (32)
	task.swapNibbles(2);
}

Output

 Number :  175
 Result :  250
 Number :  225
 Result :  30
 Number :  2
 Result :  32

Time Complexity

The time complexity of this algorithm is O(1) because the operations involved (bitwise AND, OR, and shifting) are constant-time operations. The algorithm runs in constant time regardless of the size of the input (which is fixed at 8 bits in this case).

Output Explanation

The program takes three test cases: 175, 225, and 2, and swaps the nibbles for each of them.

  1. For 175 (binary: 10101111), the result is 250 (binary: 11111010). The first nibble 1010 is swapped with the second nibble 1111, giving us 11111010, which is 250 in decimal.
  2. For 225 (binary: 11100001), the result is 30 (binary: 00011110). The first nibble 1110 is swapped with the second nibble 0001, giving us 00011110, which is 30 in decimal.
  3. For 2 (binary: 00000010), the result is 32 (binary: 00100000). The first nibble 0000 is swapped with the second nibble 0010, giving us 00100000, which is 32 in decimal.

The program successfully swaps the nibbles for each test case, and the output is as expected.

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