函数解

#include <iostream>
#include <string>
using namespace std;
void change(){
    string s;
    cin >> s;
    int len = s.size();
    for(int i = 0; i < len; i++){
        if(s[i] >= 'A' && s[i] <= 'Z'){
            s[i] += 32;
        }else if(s[i] >= 'a' && s[i] <= 'z'){
            s[i] -= 32;
        }
    }
    cout << s;
    return ;
}
int main(){
    change();
    return 0;
}