Fixato bug e implementato alcune funzioni.

tree/binarytree/heap/ArrayListCompleteBinaryTree.java

@@ -153,7 +153,7 @@ public class ArrayListCompleteBinaryTree<E> implements CompleteBinaryTree<E> {
 
 
      // internal class
-    protected static class BTPos<E> implements Position<E> {
+    public static class BTPos<E> implements Position<E> {
         E element; int index;
 
         public BTPos(E elt, int i) {