prime-number-of-set-bits-in-binary-representation.go

package problem0762

func countPrimeSetBits(L int, R int) int {
	primes := [...]int{2: 1, 3: 1, 5: 1, 7: 1, 11: 1, 13: 1, 17: 1, 19: 1}

	res := 0
	for i := L; i <= R; i++ {
		bits := 0
		for n := i; n > 0; n >>= 1 {
			bits += n & 1
		}
		res += primes[bits]
	}

	return res
}