알고리즘입문(Java) - Array -5.소수 (에라토스테네스 체)

(풀이)

 

import java.util.*;
class Main {
    public int solution(int n){
        int cnt=0;
        int[] ch = new int[n+1];
        for(int i=2; i<=n; i++){
            if(ch[i]==0){
                cnt++;
                for(int j=i; j<=n; j=j+i) ch[j]=1;
            }
        }
        return cnt;
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n=kb.nextInt();
        System.out.println(T.solution(n));
    }
}