Count primes below n

Return how many prime numbers are strictly less than n. A prime has no divisors other than 1 and itself. For each candidate k, test divisors only up to √k (i.e. while d * d <= k) — once one divides k evenly, it isn't prime.

Complete countPrimes(int n) returning how many prime numbers are strictly less than n. Example: countPrimes(10) is 4 (2, 3, 5, 7).

public class Primes {
    public static int countPrimes(int n) {
        return 0;   // change this
    }
}

Click Run to see the output here.

Next lesson →

Count primes below n

Count primes below n

Sign in

Log in or create account