C++ Tutorial/Data Types/Your Queue

A template queue class.

<source lang="cpp">#include <iostream> using namespace std;

const int maxQsize = 100;

template <class QType> class Queue {

 QType q[maxQsize]; 
 int size; 
 int enqueueloc, dequeueloc;

public:

 Queue(int len) { 
   if(len > maxQsize) 
      len = maxQsize; 
   else if(len <= 0) 
      len = 1;  

   size = len; 
   enqueueloc = dequeueloc = 0; 
 } 

 void enqueue(QType data) { 
   if(enqueueloc == size) { 
     cout << " -- Queue is full.\n"; 
     return; 
   } 
    
   enqueueloc++; 
   q[enqueueloc] = data; 
 } 

 QType dequeue() { 
   if(dequeueloc == enqueueloc) { 
     cout << " -- Queue is empty.\n"; 
     return 0;  
   } 
  
   dequeueloc++; 
   return q[dequeueloc]; 
 } 

};

int main() {

 Queue<int> intQueue1(10), intQueue2(10);  // create two integer queues 

 intQueue1.enqueue(1); 
 intQueue1.enqueue(2); 
 intQueue1.enqueue(3); 

 intQueue2.enqueue(10); 
 intQueue2.enqueue(20); 
 intQueue2.enqueue(30); 

 cout << "Contents of integer queue intQueue1: "; 
 for(int i=0; i < 3; i++) 
   cout << intQueue1.dequeue() << " "; 
 cout << endl; 

 cout << "Contents of integer queue intQueue2: "; 
 for(int i=0; i < 3; i++) 
   cout << intQueue2.dequeue() << " "; 
 cout << endl; 

 Queue<double> doubleQueue1(10), doubleQueue(10);  // create two double queues


 doubleQueue1.enqueue(1.01); 
 doubleQueue1.enqueue(2.02); 
 doubleQueue1.enqueue(3.03); 

 doubleQueue.enqueue(10.01); 
 doubleQueue.enqueue(20.02); 
 doubleQueue.enqueue(30.03); 

 cout << "Contents of double queue doubleQueue1: "; 
 for(int i=0; i < 3; i++) 
   cout << doubleQueue1.dequeue() << " "; 
 cout << endl; 

 cout << "Contents of double queue doubleQueue: "; 
 for(int i=0; i < 3; i++) 
   cout << doubleQueue.dequeue() << " "; 
 cout << endl; 

 return 0; 

}</source>

Contents of integer queue intQueue1: 1 2 3
Contents of integer queue intQueue2: 10 20 30
Contents of double queue doubleQueue1: 1.01 2.02 3.03
Contents of double queue doubleQueue: 10.01 20.02 30.03

queue class.

<source lang="cpp">#include <iostream>

 using namespace std;
 class queue {  
   int q[100];  
   int sloc, rloc;  
 public:  
   void init(void);  
   void qput(int i);  
   int qget(void);  
 };  
      
 void queue::init(void)  
 {  
   rloc = sloc = 0;  
 }  
      
 void queue::qput(int i)  
 {  
   if(sloc==100) {  
     cout << "queue is full";  
     return;  
   }  
   sloc++;  
   q[sloc] = i;  
 }  
      
 int queue::qget(void)  
 {  
   if(rloc == sloc) {  
     cout << "queue underflow";  
     return 0;  
   }  
   rloc++;  
   return q[rloc];  
 }  
      
 main(void)  
 {  
   queue a, b;
      
   a.init();  
   b.init();  
      
   a.qput(10);  
   b.qput(19);  
      
   a.qput(20);  
   b.qput(1);  
      
   cout << a.qget() << endl;  
   cout << a.qget() << endl;  
   cout << b.qget() << endl;  
   cout << b.qget() << endl;  
      
   return 0;  
 }</source>