hashset判断字符是否出现
public class Main{
public static void main(String[] args){
Scanner sc=new Scanner(System.in);
String s=sc.nextLine();
int ans=0;
HashSet<Character> st=new HashSet<>();
for(int i=0;i<s.length();i++){
if(st.contains(s.charAt(i)))continue;
st.add(s.charAt(i));
ans++;
}
System.out.print(ans);
}
}