#include <iostream>
#include <cstdio>
#include <cstring>
#define MAXN 21
using namespace std;
char str[MAXN];
int main()
{
cin>>str;
for(int i = 0; i < strlen(str); i++)
{
if(islower(str[i]))
str[i] = toupper(str[i]);
else if(isupper(str[i]))
str[i] = tolower(str[i]);
}
cout<<str;
return 0;
}
大小写转换-------蓝桥杯
原文：http://blog.csdn.net/u012965373/article/details/44905415
