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Prime Checker

  • tobeannouncd
     + 0 comments

    Since the locked code involves repeat checks of primailty, I factored in some caching so the code doesn't have to repeatedly check values.

    class Prime{
    private static Set<Integer> prime_list = new HashSet<>();

    public void checkPrime(int ... nums) {
        for (int num : nums) {
            if (prime_list.contains(num)) {
                System.out.print(num + " ");
            } else if (isPrime(num)) {
                prime_list.add(num);
                System.out.print(num + " ");
            }
        }
        System.out.println();
    }

    private static boolean isPrime(int n) {
        if (n < 2) return false;
        else if (n < 4) return true;
        else if (n % 2 == 0) return false;
        
        int sqrt = (int) Math.sqrt(n);
        for (int i = 3; i <= sqrt; i += 2) {
            if (n % i == 0) return false;
        }
        return true;
    }
}