找出 . 符号的规律，根据规律循环AC。

#include<iostream>
using namespace std;
int main()
{
    int n,i,j,k,l;
    cin>>n;
    char ch='A',sh='.',zh;
    for (i=0,j=n-2;i<n-1,j>=0;i++,j--)
    {
        for (k=0;k<i;k++)
        cout<<sh;
        cout<<ch;
        for (l=j;l>0;l--)
        cout<<sh;
        cout<<ch;
        for (l=j;l>0;l--)
        cout<<sh;
        cout<<ch;
        for (k=0;k<i;k++)
        cout<<sh;

        ch++;
        cout<<endl;
    }
    ch='A';
    for (i=0;i<n-1;i++)
    {
        cout<<ch;
        ch++;
    }
    zh=ch;
    for (i=0;i<n;i++)
    {
        cout<<ch;
        ch--;
    }
    ch=zh-1;
    cout<<endl;
    for (j=0,i=n-2;j<n-1,i>=0;j++,i--)
    {
        for (k=0;k<i;k++)
        cout<<sh;
        cout<<ch;
        for (l=j;l>0;l--)
        cout<<sh;
        cout<<ch;
        for (l=j;l>0;l--)
        cout<<sh;
        cout<<ch;
        for (k=0;k<i;k++)
        cout<<sh;

        ch--;
        cout<<endl;
    }
}