// CSE 143, Winter 2009, Marty Stepp
// A HashIntSet implements a set of integers using a hash table.
// This provides O(1) average time to add, remove, and search.  (Wow!)

import java.util.LinkedList;
import java.util.List;

public class HashIntSet {
    private static final int DEFAULT_CAPACITY = 131377;   // some arbitrary large number
    
    // "hash table" - an array of hash "buckets" where values can be stored
    private List<Integer>[] hashTable;
    
    // Creates a new empty set with a hash table of default capacity.
    public HashIntSet() {
        this(DEFAULT_CAPACITY);
    }
    
    // Creates a new empty set with the given capacity.
    // Precondition: capacity > 0
    // The  @SuppressWarnings("unchecked")  below is to avoid a compiler warning
    // for casting to a generic type. 
    @SuppressWarnings("unchecked")
    public HashIntSet(int capacity) {
        hashTable = (List<Integer>[]) (new List[capacity]);
        for (int i = 0; i < hashTable.length; i++) {
            hashTable[i] = new LinkedList<Integer>();
        }
    }
    
    // Adds the given value to this set.  If it is already contained in
    // this set, no change is made, because sets do not allow duplicates.
    public void add(int value) {
        if (!contains(value)) {
            int index = value % hashTable.length;
            hashTable[index].add(value);
        }
    }
    
    // Returns true if the given value is contained in this set.
    public boolean contains(int value) {
        int index = value % hashTable.length;
        return hashTable[index].contains(value);
    }
    
    // Removes the given value from this set if it is contained in the set.
    // If the value is not contained in the set, no change is made.
    public void remove(int value) {
        int index = value % hashTable.length;
        hashTable[index].remove((Integer) value);
    }
}