import java.util.List;
import java.util.Random;
import java.util.Arrays;
import java.util.HashMap;
import java.util.ArrayList;
public class Program
{
HashMap<Integer, Integer> hm;
List<Integer> list;
public Program() {
hm = new HashMap<>();
list = new ArrayList<>();
}
public boolean insert(int val) {
if (hm.containsKey(val))
return false;
list.add(val);
hm.put(val, list.size() - 1);
return true;
}
public boolean remove(int val) {
if (hm.containsKey(val)) {
int last = list.get(list.size() - 1);
hm.put(last,hm.get(val));
list.set(hm.get(val), last);
list.remove(list.size() - 1);
hm.remove(val);
return true;
}
return false;
}
public static int generateRandomInteger(int min, int max) {
return new Random().nextInt(max - min + 1) + min;
}
public int getRandom() {
int rnd = (int)(generateRandomInteger(0, list.size()));
return list.get(rnd);
}
public void print() {
System.out.println(Arrays.toString(list.toArray()));
}
public static void main(String[] args) {
Program obj = new Program();
obj.insert(6);
obj.insert(9);
obj.insert(8);
obj.insert(2);
obj.insert(1);
System.out.println(obj.getRandom());
obj.remove(2);
obj.print();
}
}
/*
run:
9
[6, 9, 8, 1]
*/
