判断字符类型且注意头文件

#include <bits/stdc++.h>
using namespace std;
int main(){
char a;
cin >> a;
if(int(a)>=65 && int(a)<=90){
cout << "A";
}else if(int(a)>=97 && int(a)<=122){
cout << "a";
}else if(int(a)>=48 && int(a)<=57){
cout << "0";
}else{
cout << "other";
}
return 0;
}