How to find number of trailing zeros in a binary number?
I took the K&R bitcount example for finding the number of ones in a binary number and I modified it to find the trailing number of trailing zeros:
int bitcount(unsigned x)
{
int b;
for(b=0;x!=0;x>>=1)
{
if(x&01)
break;
else
b++;
}
}
I would like to have this method reviewed.
From https://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightParallel, here's a way to compute the count in parallel for better efficiency:
unsigned int v; // 32-bit word input to count zero bits on right
unsigned int c = 32; // c will be the number of zero bits on the right
v &= -signed(v);
if (v) c--;
if (v & 0x0000FFFF) c -= 16;
if (v & 0x00FF00FF) c -= 8;
if (v & 0x0F0F0F0F) c -= 4;
if (v & 0x33333333) c -= 2;
if (v & 0x55555555) c -= 1;