package popcount
// pc[i] is the population count of i.
var pc [256]byte
func init() {
for i := range pc {
pc[i] = pc[i/2] + byte(i&1)
}
}
// PopCount returns the population count (number of set bits) of x.
func PopCount(x uint64) int {
return int(pc[byte(x>>(0*8))] +
pc[byte(x>>(1*8))] +
p