Question

How to swap two bits of a number in C

Answer 1

#include <stdio.h>
 
void showBits(int n, int size) {
    for (int i = 1 << size - 1; i > 0; i = i / 2)
        (n & i) ? printf("1") : printf("0");
}
 
int swap2Bits(unsigned int num, unsigned int firstPos, unsigned int secondPos) {
    unsigned int firstBit = (num >> firstPos) & 1;
 
    unsigned int secondBit = (num >> secondPos) & 1;
 
    unsigned int xorBit = (firstBit ^ secondBit);
 
    xorBit = (xorBit << firstPos) | (xorBit << secondPos);
 
    return num ^ xorBit;
}
  
int main()
{
    int n = 27;
     
    showBits(n, 8);
 
    int result = swap2Bits(n, 1, 6);
     
    printf("\n");
     
    showBits(result, 8);
     
    return 0;
}
 
 
 
 
/*
run:
 
00011011
01011001
 
*/

 

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