按正反顺序输出26个大写英文字母

ABCDEFGHIJKLMNOPQRSTUVWXYZ
ZYXWVUTSRQPONMLKJIHGFEDCBA

for (int i=65;i<91;i++)
cout<<(char)i;
cout<<endl;
for (int i=90;i>64;i--)
cout<<(char)i;
cout<<endl;

for(i=65;i<=90;i++)
printf("%c",i);
for(i=90;i>=65;i--)
printf("%c",i);

#include <stdio.h>

void ou(char c)
{
if (c<='Z') {
putchar(c);
ou(c+1);
}
if (c>'Z') {putchar ('\n');return;}
putchar(c);
}

int main(void)
{
ou('A');
putchar('\n');
return 0;
}