package username.graph;

import java.util.Vector;

/**
 * A simple implementation of markers.
 *
 * @author Samuel A. Rebelsky
 * @version 1.0 of April 2006
 */
public class SimpleMarker<T>
  implements Marker<T>
{
// +--------+------------------------------------------------------------
// | Fields |
// +--------+

  /**
   * A Vector that represents the marks.  marks[v] holds only when 
   * v is marked.
   */
   Vector<T> marks;


// +--------------+------------------------------------------------------
// | Constructors |
// +--------------+

  /**
   * Build a new marker that supports graphs of size _size.
   */
  public SimpleMarker(int _size)
  {
    this.marks = new Vector<T>(_size);
    this.marks.setSize(_size);
  } // SimpleMarker(int)


// +-----------+---------------------------------------------------------
// | Observers |
// +-----------+

  public boolean isMarked(int v)
  {
    return (v < this.marks.size()) && (this.marks.get(v) != null);
  } // isMarked(int)

  public T getMark(int v)
  {
    return this.marks.get(v);
  } // getMark(int)


// +----------+----------------------------------------------------------
// | Mutators |
// +----------+

  public void mark(int v, T mark)
    throws Exception
  {
    if (v < this.marks.size()) {
      this.marks.set(v,mark);
    }
    else {
      throw new Exception("Invalid vertex: " + v);
    }
  } // mark(int, T)

  public void unmark(int v)
  {
    if (v < this.marks.size()) {
      this.marks.set(v,null);
    }
  } // unmark(int)
} // class SimpleMarker<T>