可以不用ASCII码表

#include<iostream>
using namespace std;
int main(){
char a;
cin>>a;
if(a>='a'&&a<='z'){
cout<<"a"<<endl;
}else if(a>='A'&&a<='Z'){
cout<<"A"<<endl;
}else if(a>='0'&&a<='9'){
cout<<0<<endl;
}else{
cout<<"other";
}

return 0;

}