97 lines
2.5 KiB
C++
97 lines
2.5 KiB
C++
// queuetp.h -- queue template with a nested class
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#ifndef QUEUETP_H_
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#define QUEUETP_H_
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template <class Item>
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class QueueTP
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{
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private:
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enum {Q_SIZE = 10};
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// Node is a nested class definition
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class Node
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{
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public:
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Item item;
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Node * next;
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Node(const Item & i):item(i), next(0){ }
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};
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Node * front; // pointer to front of Queue
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Node * rear; // pointer to rear of Queue
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int items; // current number of items in Queue
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const int qsize; // maximum number of items in Queue
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QueueTP(const QueueTP & q) : qsize(0) {}
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QueueTP & operator=(const QueueTP & q) { return *this; }
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public:
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QueueTP(int qs = Q_SIZE);
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~QueueTP();
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bool isempty() const
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{
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return items == 0;
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}
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bool isfull() const
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{
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return items == qsize;
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}
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int queuecount() const
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{
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return items;
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}
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bool enqueue(const Item &item); // add item to end
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bool dequeue(Item &item); // remove item from front
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};
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// QueueTP methods
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template <class Item>
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QueueTP<Item>::QueueTP(int qs) : qsize(qs)
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{
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front = rear = 0;
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items = 0;
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}
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template <class Item>
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QueueTP<Item>::~QueueTP()
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{
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Node * temp;
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while (front != 0) // while queue is not yet empty
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{
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temp = front; // save address of front item
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front = front->next;// reset pointer to next item
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delete temp; // delete former front
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}
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}
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// Add item to queue
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template <class Item>
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bool QueueTP<Item>::enqueue(const Item & item)
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{
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if (isfull())
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return false;
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Node * add = new Node(item); // create node
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// on failure, new throws std::bad_alloc exception
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items++;
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if (front == 0) // if queue is empty,
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front = add; // place item at front
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else
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rear->next = add; // else place at rear
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rear = add; // have rear point to new node
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return true;
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}
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// Place front item into item variable and remove from queue
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template <class Item>
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bool QueueTP<Item>::dequeue(Item & item)
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{
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if (front == 0)
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return false;
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item = front->item; // set item to first item in queue
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items--;
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Node * temp = front; // save location of first item
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front = front->next; // reset front to next item
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delete temp; // delete former first item
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if (items == 0)
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rear = 0;
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return true;
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}
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#endif
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