/**
 * Interface for a simple priority queue for objects with integer key values
 */
public interface PriorityQueue {
  
  /**
   * Return the size of this queue
   * @return the number of items inserted and not yet removed from the queue
   */
  public int size();
  
  /**
   * Insert a new item in the queue
   * @param value item to be inserted into the queue
   * @param key priority of this item
   */
  public void insert(Object value, int key);
  
  /**
   * Return the item at the front of the queue without removing it
   * @return the item with the smallest priority in the queue
   */
  public Object min();
  
  /**
   * Remove the item at the front of the queue
   * @return the item with the smallest priority that was in the queue
   */
  public Object removeMin();
  
  /**
   * Change the priority of an item that is in the queue
   * @param value must be an object that is in the queue
   * @param newkey the new priority for this item
   */
  public void replaceKey(Object value, int newkey);
  
}