c语言问题，一起解答吧

Question

求出1-n中的所有素数(2<=n<=1000000)

Answer 1

#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>
#include<math.h>

int isPrime(int n) {
    for (int i = 2; i < sqrt(n) + 1; i++) {
        if (n % i == 0)
            return 0;
    }
    return 1;
}


int main() {
    int n, count = 0;
    scanf("%d", &n);
    for (int i = n; i > 3; i--)
        if (isPrime(i))
            if (isPrime(i - 2))
                printf("%d ", i);
    return 0;
}