81 lines
2.0 KiB
C++
81 lines
2.0 KiB
C++
// queue.cpp -- Queue and Customer methods
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#include "queue.h"
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#include <cstdlib> // (or stdlib.h) for rand()
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// Queue methods
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Queue::Queue(int qs) : qsize(qs)
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{
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front = rear = NULL; // or nullptr
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items = 0;
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}
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Queue::~Queue()
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{
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Node * temp;
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while (front != NULL) // 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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bool Queue::isempty() const
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{
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return items == 0;
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}
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bool Queue::isfull() const
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{
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return items == qsize;
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}
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int Queue::queuecount() const
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{
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return items;
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}
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// Add item to queue
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bool Queue::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; // create node
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// on failure, new throws std::bad_alloc exception
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add->item = item; // set node pointers
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add->next = NULL; // or nullptr;
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items++;
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if (front == NULL) // 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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bool Queue::dequeue(Item & item)
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{
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if (front == NULL)
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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 = NULL;
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return true;
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}
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// customer method
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// when is the time at which the customer arrives
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// the arrival time is set to when and the processing
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// time set to a random value in the range 1 - 3
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void Customer::set(long when)
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{
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processtime = std::rand() % 3 + 1;
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arrive = when;
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}
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