codeforces水题100道 第二十六题 Codeforces Beta Round #95 (Div. 2) A. cAPS lOCK (strings)

#include <cstdio>
#include <cstring>
char s[110];
bool islow(char c)
{
    return c >= ‘a‘ && c <= ‘z‘;
}
char up(char c)
{
    return c - 32;
}
char low(char c)
{
    return c + 32;
}
bool check()
{
    char *t = s;
    t ++;
    while (*t)
    {
        if (islow(*t))
            return true;
        t ++;
    }
    return false;
}
int main()
{
    scanf("%s", s);
    if (check())
    {
        puts(s);
    }
    else
    {
        char *t = s;
        while (*t)
        {
            if (islow(*t))
                putchar(up(*t));
            else
                putchar(low(*t));
            t ++;
        }
    }
    return 0;
}