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?
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;
}