C语言 函数题 想了解代码或思路

Question

Answer 1

#include <stdio.h>

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

int main()
{
    int i,n,cnt = 0;
    scanf("%d",&n);
    for(i = 1;i <= n;i++){
        if(isPrime(i)){
            printf("%d ",i);
            cnt ++;
        }
    }
    printf("\n共有%d个素数\n",cnt);
    return 0;
}