Algorithm Sedgewick Fourth Edition-1th Chapter Foundation-151 stack only retains the last pointer

1 /*************************************************************************2  *3 * A generic queue, implemented using A *circular* linked list.4 * (Exercise 1.3.29)5  *6 *% java ex_1_3_29 < tobe.txt7 * To IS or not to is (2 left on queue)8  *9  *************************************************************************/Ten  One ImportJava.util.Iterator; A Importjava.util.NoSuchElementException; -  -  Public classEx_1_3_29<item>ImplementsIterable<item> { the     Private intN; -     PrivateNode last; -  -     Private classNode { +         Privateitem Item; -         PrivateNode Next; +     } A  at    /** - * Create an empty queue. -      */ -      Publicex_1_3_29 () { -Last =NULL; -     } in  -    /** to * is the queue empty? +      */ -      Public BooleanIsEmpty () { the         returnlast = =NULL; *     } $ Panax Notoginseng    /** - * Return the number of items in the queue. the      */ +      Public intsize () { A         returnN;  the     } +  -    /** $ * Return The item least recently added to the queue. $ * Throw An exception if the queue is empty. -      */ -      PublicItem Peek () { the         if(IsEmpty ())Throw NewRuntimeException ("Queue underflow"); -         returnLast.next.item;Wuyi     } the  -    /** Wu * ADD the item to the queue. -      */ About      Public voidEnqueue (item item) { $Node x =NewNode (); -X.item =item; -         if(IsEmpty ()) -X.next =x; A         Else +         { theX.next =Last.next; -Last.next =x; $         } theLast =x; then++; the     } the  -    /** in * Remove and return the item on the queue least recently added. the * Throw An exception if the queue is empty. the      */ About      PublicItem dequeue () { the         if(IsEmpty ())Throw NewRuntimeException ("Queue underflow"); theItem item =Last.next.item; the         if(Last.next = =Last ) +Last =NULL; -         Else theLast.next =Last.next.next;Bayin--; the         returnitem; the     } -  -    /** the * Return string representation. the      */ the      PublicString toString () { theStringBuilder s =NewStringBuilder (); -          for(Item Item: This) theS.append (item + "")); the         returns.tostring (); the     } 94   the  the    /** the * Return An iterator this iterates over the items on the ' queue ' in FIFO order.98      */ About      PublicIterator<item>iterator () { -         return NewListiterator (); 101     }102 103     Private classListiteratorImplementsIterator<item> {104         Private intn =N; the         PrivateNode current =Last ;106 107          Public BooleanHasnext () {returnn > 0; }108          Public voidRemove () {Throw Newunsupportedoperationexception (); }109  the          PublicItem Next () {111             if(!hasnext ())Throw Newnosuchelementexception (); theItem item =Current.next.item;113Current =Current.next; then--; the             returnitem; the         }117     }118 119  -      Public Static voidMain (string[] args) {121ex_1_3_29<string> q =NewEx_1_3_29<string>();122          while(!Stdin.isempty ()) {123String item =stdin.readstring ();124             if(!item.equals ("-") ) Q.enqueue (item); the             Else if(!q.isempty ()) Stdout.print (Q.dequeue () + "");126         }127Stdout.println ("(" + q.size () + "left on queue: [" + Q + "])"); -     }129}

Algorithm Sedgewick Fourth Edition-1th Chapter Foundation-151 stack only retains the last pointer