import SimpleMap;

class HashTable implements SimpleMap {
    private int chains;                 // Size of table. chains= maxN/5
    private HashNode[] heads;           // Ref to 1st object in chain
    private int actual;                 // No of objects in table
    
    public HashTable(int c) {
        chains= c;
        heads= new HashNode[chains];    // Initialized to nulls
        actual= 0;
    }
    
    public int tableSize() {            // Returns no of chains, not no of objects in hash table
        return chains;
    }
    
    public int dataSize() {
        return actual;
    }
    
    public Object get(Object k) {
        if (k== null)
            return null;
        int index= Math.abs(k.hashCode()) % chains;        // Simple version
        HashNode curr= heads[index];
        while (curr != null) {
            if (curr.key.equals(k))
                return curr.value;
            curr= curr.next;
        }
        return null;
    }
    
    public Object put(Object k, Object v) {
        if (k==null || v==null)
            return null;
        int index= Math.abs(k.hashCode()) % chains;        // Simple; rehash for better performance
        HashNode curr= heads[index];
        while (curr != null) {
            if (curr.key.equals(k))
                break;
            curr = curr.next;
        }       
        if (curr == null) {
            actual++;
            heads[index]= new HashNode(k, v, heads[index]);
            return null;
        }
        else {
            Object ret = curr.value;
            curr.value = v;
            return ret;
        }        
    }
    
    public Object remove(Object k) {
        if (k== null)
            return null;
        int index = Math.abs(k.hashCode()) % chains;
        HashNode curr= heads[index];            // Simple version
        HashNode prev= null;
        while (curr != null )  {
            if (curr.key.equals(k)) {
                actual--;
                // Are we removing the head of chain
                if ( prev == null )
                    heads[index] = curr.next;
                else
                    prev.next = curr.next;
                return curr.value;
            }
            prev= curr;
            curr= curr.next;
        }
        return null;
    }
                
    public void clear() {
        for (int i=0; i < chains; i++)
            heads[i]= null;
    }
}

class HashNode {
    Object value;               // Package scope
    Object key;                 // Package scope
    HashNode next;              // Package scope
    public HashNode(Object k, Object v, HashNode t) {
        key= k;
        value= v;
        next= t;
    }
}