data_structures_free

net/datastructures/NodeDeque.java

@@ -0,0 +1,113 @@
+package net.datastructures;
+ /**
+  * Implementation of the Deque interface by means of a doubly linked
+  * list.  This class uses class DLNode, which implements a node of
+  * the list.
+  *   
+  * @author Natasha Gelfand
+  * @author Roberto Tamassia
+  */
+
+//begin#fragment NodeDeque
+public class NodeDeque<E> implements Deque<E> {
+  protected DLNode<E> header, trailer;  // sentinels
+  protected int size;    // number of elements
+//end#fragment NodeDeque
+  /** Creates an empty deque. */
+//begin#fragment NodeDeque
+  public NodeDeque() {  // initialize an empty deque
+    header = new DLNode<E>();
+    trailer = new DLNode<E>();
+    header.setNext(trailer);  // make header point to trailer
+    trailer.setPrev(header);  // make trailer point to header
+    size = 0;
+  }
+  //end#fragment NodeDeque
+    
+/** 
+ * Return the size of the deque, that is the number of elements it has. 
+ * @return  Number of elements in the deque
+ */
+ //begin#fragment size
+  public int size() {   
+    return size;
+  }
+  //end#fragment size
+    
+/** 
+ * This function returns true if and only if the deque is empty 
+ * @return  true if the deque is empty, false otherwise
+ */
+ //begin#fragment isEmpty
+  public boolean isEmpty() {    
+    if (size == 0)
+      return true;
+    return false;
+  }
+ //end#fragment isEmpty
+
+/** 
+ * Inspect the first element without modifying the deque.
+ * @return The first element in the sequence
+ */    
+ //begin#fragment first
+  public E getFirst() throws EmptyDequeException {  
+    if (isEmpty())
+      throw new EmptyDequeException("Deque is empty.");
+    return header.getNext().getElement();
+  }
+ //end#fragment first
+ 
+  public E getLast() throws EmptyDequeException { 
+    if (isEmpty())
+      throw new EmptyDequeException("Deque is empty.");
+    return trailer.getPrev().getElement();
+  }
+
+  //begin#fragment addFirst
+  public void addFirst(E o) {  
+    DLNode<E> second = header.getNext();
+    DLNode<E> first = new DLNode<E>(o, header, second);
+    second.setPrev(first);
+    header.setNext(first);
+    size++;
+  }
+  //end#fragment addFirst
+
+  public void addLast(E o) {  
+    DLNode<E> secondtolast = trailer.getPrev();
+    DLNode<E> last = new DLNode<E>(o, secondtolast, trailer);
+    secondtolast.setNext(last);
+    trailer.setPrev(last);
+    size++;
+  }
+
+  public E removeFirst() throws EmptyDequeException {
+    if (isEmpty())
+      throw new EmptyDequeException("Deque is empty.");
+    DLNode<E> first = header.getNext();
+    E o = first.getElement();
+    DLNode<E> second = first.getNext();
+    header.setNext(second);
+    second.setPrev(header);
+    size--;
+    return o;
+   }
+
+  //begin#fragment removeLast
+  public E removeLast() throws EmptyDequeException {
+    if (isEmpty())
+      throw new EmptyDequeException("Deque is empty.");
+    DLNode<E> last = trailer.getPrev();
+    E o = last.getElement();
+    DLNode<E> secondtolast = last.getPrev();
+    trailer.setPrev(secondtolast);
+    secondtolast.setNext(trailer);
+    size--; 
+    return o;
+  }
+  //end#fragment removeLast
+
+//begin#fragment tail
+}
+//end#fragment tail