using System;
using System.Collections;

public class ObjectSet {

  private int capacity;
  private static int DefaultCapacity = 10;
  private Object[] store;
  private int next;

  public ObjectSet(int capacity){
    this.capacity = capacity;
    store = new Object[capacity];
    next = 0;
  }

  public ObjectSet(): this(DefaultCapacity){
  }

  public ObjectSet(Object[] elements): this(elements.Length){
    foreach(Object el in elements) this.Insert(el);
  }

  // Copy constructor
  public ObjectSet(ObjectSet s): this(s.capacity){
    foreach(Object  el in s) this.Insert(el);
  }

  public bool Member(Object  element){
    for(int idx = 0; idx < next; idx++)
      if (element.Equals(store[idx]))
        return true;
    return false;
  }

  public void Insert(Object  element){
    if (!this.Member(element)){
      if (this.Full){
        Console.WriteLine("[Resize to {0}]", capacity * 2);
        Array.Resize<Object>(ref store, capacity * 2);
        capacity = capacity * 2;
      }
      store[next] = element;
      next++;
    }
  }

  public void Delete(Object  element){
    bool found = false;
    int  foundIdx = 0;
    for(int idx = 0; !found && (idx < next); idx++){
      if (element.Equals(store[idx])){
         found = true;
         foundIdx = idx;
      }
    }
    if (found){   // shift remaining elements left
      for(int idx = foundIdx+1; idx < next; idx++)
        store[idx-1] = store[idx];
      store[next-1] = default(Object  );
      next--;
    }
  }

  public int Count{
    get{
      return next;
    }
  }

  // Is this set a subset of other
  public bool Subset(ObjectSet other){
    foreach(Object  e in this)
      if (!other.Member(e))
         return false;
    return true;
  }
     
  public override string ToString(){
    string elRes = "";
    for(int idx = 0; idx < next; idx++) 
      elRes += " " + store[idx];
    return "{" + elRes + " "+ "}";
  }

  private bool Full{
    get{
      return next == capacity;
    }
  }

  public IEnumerator GetEnumerator (){
    return new SetEnumerator(this);
  }
  
  private class SetEnumerator: IEnumerator{
 
    private readonly ObjectSet set; 
    private int idx;

    public SetEnumerator (ObjectSet s){
      this.set = s;
      idx = -1;   // position enumerator outside range
    }
 
    public Object  Current{ 
      get {
       return set.store[idx];
      }
    }

    public bool MoveNext(){
      if (idx < set.next - 1){
        idx++; 
        return true;
      }
      else
         return false;
    }

    public void Reset(){
      idx = -1;         
    }

    public void Dispose(){
    }

  }    
   
}