// CSE 143, Winter 2010, Marty Stepp
// This class implements a set using a "hash table" array.
// The hash table stores each integer at a particular given index based
// on a "hashing function" represented by the 'bucket' method.
// This provides O(1) average time to add, remove, and search.  (Wow!)

import java.util.*;   // for LinkedList

public class HashIntSet {
    private static final int DEFAULT_CAPACITY = 100;
    
    // "hash table" - an array of hash "buckets" where values can be stored
    private List<Integer>[] elementData;
    
    // 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
    public HashIntSet(int capacity) {
        elementData = (LinkedList<Integer>[]) (new LinkedList[capacity]);
    }
    
    // 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 (elementData[bucket(value)] == null) {
            elementData[bucket(value)] = new LinkedList<Integer>();
        }
        if (!contains(value)) {
            elementData[bucket(value)].add(value);   // store 34 at index 4
        }
    }
    
    // Returns true if the given value is contained in this set, else false.
    public boolean contains(int value) {
        if (elementData[bucket(value)] != null) {
            return elementData[bucket(value)].contains(value);
        } else {
            return false;
        }
    }
    
    // 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) {
        if (elementData[bucket(value)] != null) {
            elementData[bucket(value)].remove(value);
        }
    }
    
    // helper method to perform a "hashing function" to map the given value to
    // its appropriate hash table index.
    private int bucket(int value) {
        return Math.abs(value) % elementData.length;
    }
}