data_structures_free

net/datastructures/EulerTour.java

@@ -0,0 +1,49 @@
+package net.datastructures;
+import net.datastructures.Position;
+import net.datastructures.BinaryTree;
+
+//begin#fragment EulerTour
+/** 
+  * Template for algorithms traversing a binary tree using an Euler
+  * tour. The subclasses of this class will redefine some of the
+  * methods of this class to create a specific traversal.
+  */
+public abstract class EulerTour<E, R> {
+  protected BinaryTree<E> tree;
+  /** Execution of the traversal. This abstract method must be
+   * specified in a concrete subclass. */
+  public abstract R execute(BinaryTree<E> T);
+  /** Initialization of the traversal */
+  protected void init(BinaryTree<E> T) { tree = T; }
+  /** Template method */
+  protected R eulerTour(Position<E> v) {
+    TourResult<R> r = new TourResult<R>();
+    visitLeft(v, r);
+    if (tree.hasLeft(v))
+      r.left = eulerTour(tree.left(v));		// recursive traversal
+    visitBelow(v, r);
+    if (tree.hasRight(v))
+      r.right = eulerTour(tree.right(v));	// recursive traversal
+    visitRight(v, r);
+    return r.out;
+  }
+  // Auxiliary methods that can be redefined by subclasses:
+  /** Method called for the visit on the left */
+  protected void visitLeft(Position<E> v, TourResult<R> r) {}
+  /** Method called for the visit on from below */
+  protected void visitBelow(Position<E> v, TourResult<R> r) {}
+  /** Method called for the visit on the right */
+  protected void visitRight(Position<E> v, TourResult<R> r) {}
+
+//end#fragment EulerTour
+
+//begin#fragment TourResult
+  public class TourResult<R> {
+    public R left;
+    public R right;
+    public R out; 
+  }
+//end#fragment TourResult
+//begin#fragment EulerTour
+}
+//end#fragment EulerTour