함수 primes()

1 개요

import java.util.*;
class Solution {
	static List<Integer> primes(int max) {
		boolean[] a = new boolean[max+1];
		Arrays.fill(a, Boolean.TRUE);
		int i, j;
		for(i=2; i<=Math.sqrt(max); i++) for(j=i*2; j<=max; j+=i) a[j] = false;
		List<Integer> list = new ArrayList<Integer>();
		for(i=2; i<=max; i++) if(a[i]) list.add(i);
		Collections.sort(list);
		return list;
	}
	public static void main(String[] args) {
		System.out.println( primes(1) );
		// []
		System.out.println( primes(2) );
		// [2]
		System.out.println( primes(3) );
		// [2, 3]
		System.out.println( primes(4) );
		// [2, 3]
		System.out.println( primes(5) );
		// [2, 3, 5]
		System.out.println( primes(10) );
		// [2, 3, 5, 7]
		System.out.println( primes(11) );
		// [2, 3, 5, 7, 11]
		System.out.println( primes(100) );
		// [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]
	}
}
2 같이 보기

3 참고
