题解 | #字母大小写转换#

#include <stdio.h>
#include <ctype.h>

int main()
{
    char ch = 'a';
    while (~scanf(" %c", &ch))
    {
        //判断是不是大写字母
        if (isupper(ch)) 
        {
            //转小写
            printf("%c\n",tolower(ch));
        }else if(islower(ch))
        {
             //转大写
            printf("%c\n",toupper(ch));       
        }
    }
    return 0;
}