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Unable to post SumoLogic StartUp company interview questions, if anyone can post on my behalf will be thank ful

Question 1 :

Kindly find the question below:

Design a data structure which has following operations:

1. void add(e)
2. void delete(e)
3. boolean contains(e)
4. e getRandom()
5. e getMostRecent()

All operations should be preferably O(1)

Answer :

public class ValidateData
{
private HashMap<Object, Integer> hashMap = new HashMap<>();
private ArrayList<Object> list;

public ValidateData()
{
hashMap = new HashMap<>();
list = new ArrayList<>();
}

public void insert(Object object)
{
int index = list.size();

hashMap.put(object, index);
list.add(object);

}

public boolean contains(Object object)
{
return hashMap.containsKey(object);
}

public void delete(Object object)
{
if (hashMap.containsKey(object))
{
int index = hashMap.get(object);
int end = list.size() - 1;
Object o = list.get(end);
list.set(index, o);
list.remove(end);
hashMap.put(o, index);
hashMap.remove(object);

}
}

public Object getRandom()
{
Random rand = new Random();
int index = rand.nextInt(list.size());
System.out.println(list.get(index));
return list.get(index);
}