**Question:** How would you find the number of bit swaps required to convert integer A to integer B?

**Answer: **Gut instinct might suggest that you go through every bit of A and every bit of B while simultaneously updating a count of the bits that are different. But how about a cooler way to solve this?

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A key to solving a lot of bit manipulation questions is the use of the XOR functionality.

int bit_swaps_required( int a, int b ) { unsigned int count = 0; for( int c = a ^ b; c != 0; c = c >> 1 ) { count += c & 1; } return count; }

Simple right?

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Perhaps this is even better?

int bit_swap_required (int a, int b)

{

unsigned int count = 0;

unsigned int c = a^b;

while (c)

{

c &= c-1;

++ count;

}

return count;

}

Better solution: count the ones in a^b.

count = 0;

for(int c =a^b; c !=0; c &=(c-1), count++);

Thanks, good catch. I’ve updated the post.

Hi, a slip of the pen??

int bit_swaps_required( int a, int b ) {

unsigned int count = 0;

for( int c = a ^ b; c != 0; c = c >> 1 ) {

count += c & 1;

}

return count;

}