/** Node class for skip lists.
 *  Since this is just a skeleton implementation, I'm leaving out the item
 *  of real object data.  As a result, the only "data" we're storing is the key
 *  at each node.
 *  I'm making the pointer attributes protected, so that in SkipList.java
 *  you may easily access them.
 */
public class Node
{
  protected Node up;
  protected Node down;
  protected Node left;
  protected Node right;
  private int key;
  protected int level;   // For debugging, convenient to know what row I'm on.
  
  public Node(int k, int l)
  {
    up = null;
    down = null;
    left = null;
    right = null;
    key = k;
    level = l;
  }
  
  public int getKey()
  {
    return key;
  }
  
  /**
   * Returns a user-friendly version of the key.
   * @return key or +inf or -inf
   */
  public String getOutputKey()
  {
    String prettyKey = Integer.toString(key);
    if (key == Integer.MAX_VALUE) {
      prettyKey = "+inf";
    } else if (key == Integer.MIN_VALUE) {
      prettyKey = "-inf";
    }
    
    return prettyKey;
  }
  
  // A handy method to help when debugging.
  public String toString()
  {
    StringBuilder build = new StringBuilder();
    build.append("" + this.getOutputKey() + "(");
    if (this.up != null)
      build.append("up " + this.up.getOutputKey() + " ");
    if (this.down != null)
      build.append("down " + this.down.getOutputKey() + " ");
    if (this.left != null)
      build.append("left " + this.left.getOutputKey() + " ");
    if (this.right != null)
      build.append("right " + this.right.getOutputKey() + " ");
    build.append("level " + level + ")");
    
    return build.toString();
  }
}