// Helene Martin, CSE 143
// Hash table implementation of a set, an unordered collection without duplicates.
// The hash table stores values at indexes determined by a hashing function.

// This very basic implementation has no collision resolution so it will only work 
// if all inserted values hash to unique indexes.

public class HashSetIncomplete<E> implements Set<E> {
   private int size;
   private E[] elementData;

   // Builds a new HashSet of the specified capacity
   public HashSetIncomplete(int capacity) {
      elementData = (E[]) new Object[capacity]; // don't worry about this
   }

   // Adds the given value to the set
   // Pre: There is nothing at indexOf(value)
   @Override
   public void add(E value) {
      if (!contains(value)) {
         elementData[indexOf(value)] = value;
         size++;
      }
   }

   // Remove the given value from the set
   @Override
   public void remove(E value) {
      if (contains(value)) {
         elementData[indexOf(value)] = null;
         size--;
      }
   }

   // Checks whether the given value is in the set
   @Override
   public boolean contains(E value) {
      return elementData[indexOf(value)] != null;
   }

   // Returns the size of the set
   @Override
   public int size() {
      return size;
   }

   // Uses the hashing function to find the index of a value.
   private int indexOf(E value) {
      return Math.abs(value.hashCode() % elementData.length);
   }
}