判断质数

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int prime(int num)
{
if (num == 2)
return 1;
for (int i=num-1; i >1; i–)
{
if (num%i == 0)
return 0;
}
return 1;
}
int main()
{
int num = 0;
scanf("%d", &num);
int flag = prime(num);
if (flag == 1)
printf(“It’s prime\n”);
else
printf(“It’s not prime\n”);
system(“pause”);
return 0;
}