题解 | 筛选法求素数

/*#include <stdio.h>
int main()
{
    int n;
    scanf_s("%d", &n);
    int flag = 0,count=0;
    for (int i = 2; i < n; i++)
    {
        for (int j = 1; j < i; j++)
        {
            flag = 0;
            if (i % j != 0)
            {
                flag = 1;
                break;
            }
        }
        if (flag == 0)
        {
            count++;
        }
    }
    printf("%d", count);

    return 0;
}*/
#include<stdio.h>
#include<math.h>
int main() {
    int n = 0;
    int count = 0;
    scanf("%d", &n);

    int i, j = 0;
    for (i = 2; i <= n; i++) {
        for (j = 2; j < sqrt(i); j += 1) {
            if (i % j == 0)
                break;
        }
        if (j > sqrt(i)) {
            printf("%d ", i);
            count++;
        }
    }

    printf("\n");
    printf("%d", n - count - 1); //这边我也不懂哎
}