소수찾기

package programmers;

import java.util.Arrays;

public class 소수찾기 {

   private static boolean[] isPrime;

   public static int solution(int n) {
      isPrime = new boolean[n + 1];
      Arrays.fill(isPrime, true);

      for (int i = 2; i <= Math.sqrt(n); i++) {
         if (isPrime[i]) {
            for (int j = i * i; j <= n; j += i) {
               isPrime[j] = false;
            }
         }
      }
      int answer = 0;
      for (int i = 2; i <= n; i++) {
         if (isPrime[i])
            answer++;
      }
      return answer;
   }

   public static void main(String[] args) {
      System.out.println(solution(1000000));
      System.out.println(solution(5));
   }
   
}