输出小于等于n的素数

#include<iostream>
#include<math.h>
using namespace std;
int n = 0;
void prime_number(int num)
{
	int k = 0, i = 2;
	if (num >= 0)
	{
		k = (int)sqrt((double)num);
		while (i <= k)
		{
			if (num % i == 0)
				break;
			i++;
		}
		if (i > k)
		{
			cout << num << " ";
			n++;
			if (n > 9)
			{
				cout << endl;
				n = 0;
			}
		}
	}
}
int main()
{
	int num = 0;
	cout << "输入一个大于2的正整数：" << endl;
	cin >> num;
	cout << "素数有：" << endl;
	for (int i = 2; i <= num; i++)
		prime_number(i);
}