题解 | #空心正方形图案#

#include<stdio.h>
int main()
{
	int a = 0;
	int b = 0;
	int c = 0;
	int d = 0;
	int e = 0;
	int f = 0;
	while (e<18)
	{ 
		scanf("%d", &c);
		e++;
		if(c>=3&&c<=20)
		{ 
		f = c;
		for (a = 0;a < f;a++)
		{
			for (b = 0;b < f;b++)
			{
				if (a==0||a==f-1||b==0||b==f-1)
			{
				printf("* ");
			}
			else
			{
				printf("  ");
			}	
		}
         printf("\n");
	}
		}
		else
		{
			printf("您输入有误");
				break;
		}
	} 
	return 0;
}