程序代码：

#include <stdio.h>
#include <string.h>

char a[30][30] = {0};
void draw(int n)
{
    int i,j,k;
    for(i = 1;i<=2*n-1;i++)
    {
        char x = 'A';
        char temp = 0;
        for(j = 1;j<=2*n-1;j++)
        {   
            if(i<=n)
            {
                if(j>=n-(i-1) && j<=n)
                {
                    a[i][j] = x++;
                    if(j == n)
                        temp = a[i][n];
                }
                else if(j>n && j<=n+(i-1))
                {
                    a[i][j] = --temp;
                }
                else if(j<=n)
                    a[i][j] = ' ';
            }
            else
            {
                int buf = i - 2*(i-n);
                if(j>=n-(buf-1) && j<=n)
                {
                    a[i][j] = x++;
                    if(j == n)
                        temp = a[i][n];
                }
                else if(j>n && j<=n+(buf-1))
                {
                    a[i][j] = --temp;
                }
                else if(j<=n)
                    a[i][j] = ' ';
            }
        }
    }
}
int main()
{
    int i,j,k;
    int n,m = 1;
    while(EOF != scanf("%d",&n))
    {
        if(n>26 || n<-26)
        {
            printf("No image!\n");
            continue;
        }
        int temp = n;
        if(n<0)
            n*=-1;
        memset(a,0,sizeof(a));
        printf("Case %d: n=%d\n",m++,temp);
        draw(n);
        for(i = 1;i<=2*n-1;i++)
        {
            for(j = 1;j<=2*n-1;j++)
            {
                printf("%c",a[i][j]);
            }
            printf("\n");
        }
        printf("\n");
    }
    return 0;
}