题解 | 空心正方形图案

#include <stdio.h>

int main()
{
	int n = 0; 
	while (scanf("%d", &n) != EOF)
	{
		if (n >= 3 && n <= 20)
		{
			for (int i = 0; i < n; i++)
			{
				for (int j = 0; j < n; j++)
				{
					if (i == 0 || i == n - 1 || j == 0 || j == n - 1)
					{
						printf("* ");
					}
					else
					{
						printf("  ");
					}
				}
				printf("\n");
			}
		}
		else
		{
			printf("不在输入范围\n"); 
			break; 
		}
	}
	return 0; 
}