[백준 Java] 약수, 배수와 소수 - 1978번: 소수 찾기

 

 

import java.io.*;
import java.util.StringTokenizer;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        int N = Integer.parseInt(br.readLine());
        StringTokenizer st = new StringTokenizer(br.readLine());

        int count = 0;

        while (st.hasMoreTokens()) {
            int num = Integer.parseInt(st.nextToken());
            boolean isPrime = true;

            if (num < 2) {
                isPrime = false;
            } 
            else {
                for (int i = 2; i * i <= num; i++) {
                    if (num % i == 0) {
                        isPrime = false;
                        break;
                    }
                }
            }
            if (isPrime) {
                count++;
            }
        }

        bw.write(count + "\n");

        br.close();
        bw.flush();
        bw.close();
    }
}