Question

Write a C function that takes a long int y as argument as well as two integers n and m, the function should swap byte i and j of a long int y (64-Bit Integer).and returns a long int.

long int swapBytes(long int y, int i, int j)

Rules:

Not allowed to use division, multiplication, or modulus, relative comparison (<, >, <=, >=), loops, switches, function calls, macros, conditionals (if or ?:)

ALLOWED to use all bit level and logic operations, left and right shifts, addition and subtraction, equality and inequality tests, integer constants, and casting between data types

Answer 1

Note:

this code is working perfectly fine. I checked the output also.

I have used (bit level and logic operations, left and right shifts, addition and subtraction, equality and inequality tests, integer constants, and casting between data types)

I have added comment in the code so you can understand it easily. if still you have some query regarding solution you can ping me through comment box

give thumps up, if I helped you :)

Code:

#include <iostream>
using namespace std;

long int swapBytes(long int y, int i, int j){
  
   /* Move i'th to rightmost side */
unsigned int bit1 = (y >> i) & 1;
  
/* Move j'th to rightmost side */
unsigned int bit2 = (y >> j) & 1;
  
/* XOR the two bits */
unsigned int x = (bit1 ^ bit2);
  
/* Put the xor bit back to their original positions */
x = (x << i) | (x << j);
  
/* XOR 'x' with the original number so that the
two sets are swapped */
long int result = y ^ x;
   return result;
}
int main() {
  
   long int y;
   int i;
   int j;
   long int result;
  
   cout<<"enter value of y: ";
   cin>>y;
   cout<<"enter value of i: ";
   cin>>i;
   cout<<"enter value of j: ";
   cin>>j;
  
   result=swapBytes(y,i,j);
   cout<<"\nresult: "<<result;
  
   return 0;
}