题解 | #ipv4地址白名单#

import java.util.*;
public class Main{
    public static void main(String[] args){
        String s;
        Scanner sc = new Scanner(System.in);
        HashSet<String> set = new HashSet();
        while(true){
            s = sc.next();
            if(s.equals("end"))break;
            if(s.charAt(0)=='i'){
                set.add(s.split(":")[1]);
                System.out.println("ok");
            }
            if(s.charAt(0)=='d'){
                set.remove(s.split(":")[1]);
                 System.out.println("ok");
            }
            if(s.charAt(0)=='s'){
                boolean a = set.contains(s.split(":")[1]);
                 System.out.println(a);
            }
        }
        
    }
}