백준 2906번 : 에라토스테네스의 체 [c언어]

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>


int trash[1000];
int visited[1000] = { 0, };

void toss(int start, int N, int cnt){
	int temp = 1;
	int start_cpy = start;
	if (start == N && visited[start_cpy-2]==1) return;
	if (start == N && visited[start_cpy-2]==0) {
		trash[cnt] = start_cpy;
		cnt++;
		visited[start_cpy - 2] = 1;
		return;
	}
	if (visited[start-2] == 0) {
		while (1) {
			if (start_cpy > N) break;
			
			if (visited[start_cpy - 2] != 1)
			{
				trash[cnt] = start_cpy;
				cnt++;
				visited[start_cpy - 2] = 1;
			}
			start_cpy = start_cpy + start;
		}
	}
	toss(start + 1, N, cnt);
}

int main() {
	int N = 0;
	int K = 0;



	scanf("%d", &N);
	scanf("%d", &K);

	int cnt = 0;

	toss(2, N, cnt);

	printf("%d", trash[K-1]);

	return 0;
}