PacMan/src/gr/auth/ee/dsproject/node/Tree.java

/**
 * @file MinMaxTree.java
 * @brief
 *    File containing the Pacman Min-Max Tree class.
 * 
 * @author  Christos Choutouridis   8997 cchoutou@ece.auth.gr
 * @author  Konstantina Tsechelidou 8445 konstsec@ece.auth.gr
 */
package gr.auth.ee.dsproject.node;


/**
 * @brief
 *    A tree-like data structure containing move nodes to apply the min-max
 *    algorithm.
 * @note
 *    This is NOT a real tree. We do not insert node based on a key etc...
 */
public class Tree
{
   /*
    * ============ Constructor ==============
    */
   /**
    * @brief
    *    The simple constructor. Do nothing (this is a static class)
    */
   public Tree () { }

   /*
    * ========== private helpers  ==============
    */
   private static double min (double x, double y) {
      return (x < y) ? x : y;
   }
   private static double max (double x, double y) {
      return (x > y) ? x : y;
   }

   /*
    * ========== Tree-like public methods =============
    */
   /**
    * @brief
    *    Insert a node to a parent directly.
    *    This is NOT a real tree. We do not insert node based on a key
    * @param node    Node to insert
    * @param parent  The parent in witch to insert
    * @return        Reference to inserted node
    *                If insert fail, returns null
    */
   public static Node89978445 grow (Node89978445 node, Node89978445 parent) {
      if (parent.children.add (node)) {
         node.parent = parent;
         node.depth = parent.depth + 1;
         return node;
      }
      else
         return null;
   }

   public static Node89978445 minmaxAB (Node89978445 node, int depth, double a, double b, boolean maxingPlayer)
   {
      double v, ev;
      Node89978445 vNode = null;

      if ((depth == 0) || (node.children.isEmpty()))
         return node;
      
      if (maxingPlayer) {
         v = Globals.EVAL_MIN - 1;
         for (int i=0 ; i<node.children.size() ; ++i) {
            ev = minmaxAB (node.children.get (i), depth-1, a, b, false).getEvaluation();
            if (ev > v) {
               v = ev;
               vNode = node.children.get (i);
            }
            a = max (v, a);
            if (b <= a)
               break;
         }
         return vNode;
      }
      else {
         v = Globals.EVAL_MAX + 1;
         for (int i=0 ; i<node.children.size() ; ++i) {
            ev = minmaxAB(node.children.get (i), depth-1, a, b, true).getEvaluation();
            if (ev < v) {
               v = ev;
               vNode = node.children.get (i);
            }
            b = min (v, b);
            if (b <= a)
               break;
         }
         return vNode;
      }
   }
   
}