백준알고리즘 1929번 소수 구하기

백준알고리즘

https://www.acmicpc.net/problem/1929

import java.util.Scanner;

public class Main2 {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        
        int a = scan.nextInt();
        int b = Integer.parseInt(scan.nextLine().trim());
        
        boolean[] check = new boolean[b+1];
        for(int i=0; i < check.length; i++) check[i] = true;
        
        int sqrt = (int) Math.sqrt(b);
        
        for(int i=2; i <= sqrt; i++) {
            if(check[i] == true) {
                for(int j=i; j * i <= b; j++) {
                    check[i*j] = false;
                }
            }
        }
        
        for(int i=a; i <=b; i++) {
            if(i == 1) continue;
            if(check[i]) System.out.println(i);
        }
    }
}