筛法求素数

void sieve_prime(int n)
{
	int *a = (int *)malloc((n+1) * sizeof(int));
	int i, j;
	for ( i = 0; i <= n; i++) 
			a[i] = 0;

	int cnt = sqrt(n);
	for (i = 2; i <= cnt ; i++)
	{
		if (a[i])
			continue;
		for (j = i*i; j <= n; j += i)
			a[j] = 1;
	}

	for (i = 2; i <= n; i++)
			if (a[i] == 0)
				printf("%d\n", i);
	
}