coj 1140 序号互换

进制转换，注意边界（WA 5次）。

测试数据：26 27 52 160 Z FD

结果：　　Z AA AZ FD 26 160

# include <stdio.h>
# include <ctype.h>
# include <memory.h>
 
char a[15];
char s[15];
 
int main()
{
    int T, i, n;

    scanf("%d", &T);
    while (T--)
    {
        scanf("%s", a);
        if (isdigit(a[0]))
        {
            i = 0;
            n = atoi(a);
            while  (n > 0)
            {
                s[i] = (n+25) % 26 + 'A'; 
                ++i;
                if (n % 26) n /= 26;
                else {n /= 26; --n;}
            }
            while (i > 0) putchar(s[--i]);
            putchar('\n');
            memset(s, 0, sizeof(s));
        }
        else
        {
            i = n = 0;
            while (a[i] != '\0')
            {
                n = 26*n + a[i]-'A'+1;
                ++i;
            }
            printf("%d\n", n);
        }
         
    }
     
    return 0;
}