# include <iostream>
# include <cctype>
using namespace std;
int main()
{
char ch;
cout << "Please enter a characters, I'll repeat it until '@': ";
while(cin.get(ch))
{
if(ch == '@')
break;
if(isdigit(ch))
continue;
if(isupper(ch))
ch = tolower(ch);
if(islower(ch))
ch = toupper(ch);
cout << ch;
}
cout << endl;
return 0;
}
求问上面的代码。输入小写能转换为大写 但是为什么大写转化不了小写啊？

if(isupper(ch))
ch = tolower(ch);
if(islower(ch))
ch = toupper(ch);
你好好想想，如果是大写，执行这段代码会发生什么

应该用if else 不然先转换成小写，然后又被转换成大写。。。