Data Structures Using C++ Chapter 8 Queues Data Structures Using C++

Data Structures Using C++ Chapter Objectives Learn about queues Examine various queue operations Learn how to implement a queue as an array Learn how to implement a queue as a linked list Data Structures Using C++

Data Structures Using C++ Chapter Objectives Discover queue applications Examine the STL class queue Discover priority queues Data Structures Using C++

Data Structures Using C++ Queues Definition: data structure in which the elements are added at one end, called the rear, and deleted from the other end, called the front or first First In First Out (LIFO) data structure Data Structures Using C++

Basic Operations on a Queue initializeQueue: Initializes the queue to an empty state destroyQueue: Removes all the elements from the queue, leaving the queue empty isEmptyQueue: Checks whether the queue is empty. If the queue is empty, it returns the value true; otherwise, it returns the value false Data Structures Using C++

Basic Operations on a queue isFullQueue: Checks whether the queue is full. If the queue is full, it returns the value true; otherwise, it returns the value false front: Returns the front (first) element of the queue; the queue must exist back: Returns the front (first) element of the queue; the queue must exist Data Structures Using C++

Basic Operations on a queue addQueue: Adds a new element to the rear of the queue; the queue must exist and must not be full deleteQueue: Removes the front element of the queue; the queue must exist and must not be empty Data Structures Using C++

Data Structures Using C++ Queues as Arrays Data Structures Using C++

Data Structures Using C++ Queues as Arrays Data Structures Using C++

Data Structures Using C++ Circle Queue Data Structures Using C++

Data Structures Using C++ Queues as Arrays Data Structures Using C++

Data Structures Using C++ Queues as Arrays Data Structures Using C++

Data Structures Using C++ Queues as Arrays Data Structures Using C++

Data Structures Using C++ Queues as Arrays Data Structures Using C++

Data Structures Using C++ Queues as Arrays Data Structures Using C++

Data Structures Using C++ Queues as Arrays Data Structures Using C++

Data Structures Using C++ Queues as Arrays Data Structures Using C++

UML Diagram of the class queueType Data Structures Using C++

Data Structures Using C++ Initialize Queue Definition of the function initializeQueue: template<class Type> void queueType<Type>::initializeQueue() { queueFront = 0; queueRear = maxQueueSize - 1; count = 0; } Data Structures Using C++

Empty Queue and Full Queue template<class Type> bool queueType<Type>::isEmptyQueue() { return (count == 0); } bool queueType<Type>::isFullQueue() return (count == maxQueueSize); Data Structures Using C++

Data Structures Using C++ Destroy Queue template<class Type> void queueType<Type>::destroyQueue() { queueFront = 0; queueRear = maxQueueSize - 1; count = 0; } Data Structures Using C++

Data Structures Using C++ front and back template<class Type> Type queueType<Type>::front() { assert(!isEmptyQueue()); return list[queueFront]; } template<class Type> Type queueType<Type>::back() { assert(!isEmptyQueue()); return list[queueRear]; } Data Structures Using C++

Data Structures Using C++ Add Queue template<class Type> void queueType<Type>::addQueue(const Type& newElement) { if(!isFullQueue()) queueRear = (queueRear + 1) % maxQueueSize; //use the mod //operator to advance queueRear //because the array is circular count++; list[queueRear] = newElement; } else cerr<<"Cannot add to a full queue."<<endl; Data Structures Using C++

Data Structures Using C++ Delete Queue template<class Type> void queueType<Type>::deleteQueue() { if(!isEmptyQueue()) count--; queueFront = (queueFront + 1) % maxQueueSize; //use the mod //operator to advance queueFront //because the array is circular } else cerr<<"Cannot remove from an empty queue."<<endl; Data Structures Using C++

Constructor and Destructor Creates an array of the size specified by the user Default value is 100 Initializes queueFront queueRear to indicate that the queue is empty Destructor When queue object goes out of scope, destructor reallocates memory occupied by the array that stores the queue elements Data Structures Using C++

Data Structures Using C++ Linked Queue as an ADT Data Structures Using C++

Empty, Full, and Destroy Queue Queue is empty if queueFront is NULL Queue is full only if we run out of memory Destroy queue removes all elements of the queue Data Structures Using C++

Data Structures Using C++ addQueue Adds a new element to the end of the queue Access the pointer queueRear to implement addQueue Data Structures Using C++

Front, Back, and Delete Queue If queue is nonempty: operation front returns the first element of the queue operation back returns the last element of the queue operation deleteQueue removes the first element of the queue If queue is empty: function front terminates the program function back terminates the program Data Structures Using C++

STL class queue (Queue Container Adapter) Data Structures Using C++

Data Structures Using C++ Priority Queue FIFO rules of a queue are relaxed Customers or jobs with higher priority are pushed to front of queue To implement: use an ordinary linked list, which keeps the items in order from the highest to lowest priority use a treelike structure Data Structures Using C++

Data Structures Using C++ Application of Queues Data Structures Using C++

Data Structures Using C++ Application of Queues Data Structures Using C++

Data Structures Using C++ Application of Queues Data Structures Using C++

Application of Queues: waitingCustomerQueueType Data Structures Using C++

Data Structures Using C++ Poisson Distribution Data Structures Using C++

Data Structures Using C++ Chapter Summary Queue Data Structure Restricted Version of arrays and linked list Basic operations First In First Out (FIFO) Queues Implemented as Arrays Data Structures Using C++

Data Structures Using C++ Chapter Summary Queues Implemented as Linked Lists STL class queue Priority Queues Application of Queues Data Structures Using C++