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  1. // implementation file for the queue class
  2.  
  3. #include <iostream>
  4. using namespace std;
  5.  
  6. const int queue_size = 6;
  7.  
  8. class queue
  9. {
  10.       private:
  11.          char data [queue_size]; // elements in the queue
  12.          int front, // index to the front of the queue, indexes one previous
  13.                     // to actual front element (remove)
  14.              rear;  // index of the rear element;
  15.       public:
  16.          queue ();  // create an empty queue
  17.          void enqueue (char item);   // adds an element to the rear
  18.          char dequeue ();            // removes an element from the front
  19.          bool empty ();              // returns true for an empty queue
  20.          bool full ();               // returns true for a full queue
  21.          int elements ();            // returns the number of elements in the queue
  22.          void print ();              // prints the queue from front to rear
  23. };
  24.  
  25. // returns the number of elements in the queue. If queue is empty, it returns 0.
  26. int queue::elements ()
  27. {
  28. 	int i;
  29. 	if(empty())
  30. 	return 0;
  31. 	else
  32. 	for (i = front+1; i != (rear + 1) % queue_size; i = (i + 1)%queue_size)
  33. 	return i;
  34. }
  35.  
  36. // prints the elements in the queue from first to last element. If the queue is empty, nothing
  37. // is printed
  38. void queue::print ()
  39. {
  40. 	int i;
  41. 	if(!empty())
  42. 	for (i = front+1; i != (rear + 1) % queue_size; i = (i + 1)%queue_size)
  43. 	cout << data[i] << " ";
  44. }
  45.  
  46. // constructor creates an empty queue
  47. queue::queue ()
  48. {
  49.     front = 0;
  50.     rear = 0;
  51. }
  52.  
  53. // enqueue adds an element to the rear of the queue
  54. void queue::enqueue (char item)
  55. {
  56.       // if full, can't add another element
  57.       if (full ())
  58.       {
  59.           cout << "\n\nQueue Error: Can't add to a full queue";
  60.           cout << "\nQueue will not be changed";
  61.       }
  62.       else // ok to add an item
  63.       {
  64.            rear = (rear + 1) % queue_size;
  65.            data [rear] = item;
  66.       }
  67. }
  68.  
  69. // dequeue removes an element from the front of the queue
  70. char queue::dequeue ()
  71. {
  72.      // if the queue is empty, we can't remove a value
  73.      if (empty ())
  74.      {
  75.           cout << "\n\nQueue Error: Can't remove from an empty queue";
  76.           cout << "\nReturning a blank";
  77.           return ' ';
  78.      }
  79.      else // ok to remove a value
  80.      {
  81.           front = (front + 1) % queue_size;
  82.           return data [front];
  83.      }
  84. }
  85.  
  86. // empty returns true if the queue is empty
  87. bool queue::empty ()
  88. {
  89.      return front == rear;
  90. }
  91.  
  92. // full returns true if the queue is full
  93. bool queue::full ()
  94. {
  95.      return (rear + 1) % queue_size == front;
  96. }
  97.  
  98. int main()
  99. {
  100. 	queue q;
  101. 	q.enqueue('a');
  102. 	q.enqueue('b');
  103. 	q.enqueue('c');
  104. 	q.enqueue('d');
  105. 	q.enqueue('e');
  106. 	q.print();
  107. }
  108.  
Success #stdin #stdout 0s 3140KB
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a b c d e
https://ideone.com/1rMLTr
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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