题解

AC代码

#include <bits/stdc++.h>
using namespace std;
int n;
int p[20005];

void init() {
    memset(p, true, sizeof(p));
    p[0] = p[1] = false;
    for (int i = 2; i <= sqrt(n); i++) {
        if (p[i]) {
            for (int j = i * i; j <= n; j += i) {
                p[j] = false;
            }
        }
    }
}
int main() {
    scanf("%d", &n);
    init();
    for (int i = 2; i <= n; i++) {
        if (p[i])
            printf("%d ", i);
    }
    return 0;
}