C++ Tutorial/queue stack/queue

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A queue for strings: push, empty, front, pop

#include <iostream>
#include <string>
#include <queue>
#include <stack>
using namespace std;
int main()
{
  queue<string> q;
  cout << "Pushing one two three four\n";
  q.push("one");
  q.push("two");
  q.push("three");
  q.push("four");
  cout << "Now, retrieve those values in FIFO order.\n";
  while(!q.empty()) {
    cout << "Popping ";
    cout << q.front() << "\n";
    q.pop();
  }
  cout << endl;

  return 0;
}

Instantiating an STL Queue

#include <queue>
#include <list>
int main ()
{
    using namespace std;
    // A queue of integers
    queue <int> qIntegers;
    // A queue of doubles
    queue <double> qDoubles;
    // A queue of doubles stored internally in a list
    queue <double, list <double> > qDoublesInList;
    return 0;
}

Queue buffer

#include <queue>
#include <stdexcept>
#include <iostream>
using namespace std;
using std::queue;
template <typename T>
class PacketBuffer{
 public:
  PacketBuffer(int maxSize = -1);
  void bufferPacket(const T& packet);
  T getNextPacket() throw (std::out_of_range);
 protected:
  queue<T> mPackets;
  int mMaxSize;
 private:
  PacketBuffer(const PacketBuffer& src);
  PacketBuffer& operator=(const PacketBuffer& rhs);
};
template <typename T>
PacketBuffer<T>::PacketBuffer(int maxSize)
{
  mMaxSize = maxSize;
}
template <typename T>
void PacketBuffer<T>::bufferPacket(const T& packet)
{
  if (mMaxSize > 0 && mPackets.size() == static_cast<size_t>(mMaxSize)) {
    return;
  }
  mPackets.push(packet);
}
template <typename T>
T PacketBuffer<T>::getNextPacket() throw (std::out_of_range)
{
  if (mPackets.empty()) {
    throw (std::out_of_range("Buffer is empty"));
  }
  // retrieve the head element
  T temp = mPackets.front();
  // pop the head element
  mPackets.pop();
  // return the head element
  return (temp);
}

class IPPacket {};
int main(int argc, char** argv)
{
  PacketBuffer<IPPacket> ipPackets(3);
  ipPackets.bufferPacket(IPPacket());
  ipPackets.bufferPacket(IPPacket());
  ipPackets.bufferPacket(IPPacket());
  ipPackets.bufferPacket(IPPacket());
  while (true) {
    try {
      IPPacket packet = ipPackets.getNextPacket();
    } catch (out_of_range&) {
      cout << "Processed all packets!" << endl;
      break;
    }
  }
  return (0);
}

queue.front()

#include <iostream>
using std::cout;
using std::endl;
#include <queue>
int main()
{
   std::queue< double > values;
   
   values.push( 3.2 );
   values.push( 9.8 );
   values.push( 5.4 );
   cout << "Popping from values: ";
   
   while ( !values.empty() ) 
   {
      cout << values.front() << " ";
      values.pop();
   }
   cout << endl;
   return 0;
}
Popping from values: 3.2 9.8 5.4

Queue: push, pop and size

#include <iostream>
#include <queue> 
#include <list>
using namespace std;
int main()
{
  int thedata[] = {45, 34, 56, 27, 71, 50, 62};
  queue<int, list<int> > q;  
  cout << "The queue size is now " << q.size() << endl;
  cout << "Pushing 4 elements " << endl;
  for (int i = 0; i < 4; ++i)
    q.push(thedata[i]);
  cout << "The queue size is now " << q.size() << endl;
  cout << "Popping 3 elements " << endl;
  for (int i = 0; i < 3; ++i) {
    cout << q.front() << endl;
    q.pop();
  }
  cout << "The queue size is now " << q.size() << endl;
  return 0;
}
The queue size is now 0
Pushing 4 elements
The queue size is now 4
Popping 3 elements
45
34
56
The queue size is now 1

queue: push, pop, front and size

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <queue>
#include <string>
using namespace std;
int main()
{
    queue<string> q;
    // insert three elements into the queue
    q.push("These ");
    q.push("are ");
    q.push("more than ");
    // read and print two elements from the queue
    cout << q.front();
    q.pop();
    cout << q.front();
    q.pop();
    // insert two new elements
    q.push("four ");
    q.push("words!");
    // skip one element
    q.pop();
    // read and print two elements
    cout << q.front();
    q.pop();
    cout << q.front() << endl;
    q.pop();
    // print number of elements in the queue
    cout << "number of elements in the queue: " << q.size()
         << endl;
}
These are four words!
number of elements in the queue: 0

queue with doubles

#include <iostream>
using std::cout;
using std::endl;
#include <queue>
int main()
{
   std::queue< double > values;
   
   values.push( 3.2 );
   values.push( 9.8 );
   values.push( 5.4 );
   cout << "Popping from values: ";
   
   while ( !values.empty() ) 
   {
      cout << values.front() << " ";
      values.pop();
   }
   cout << endl;
   return 0;
}
Popping from values: 3.2 9.8 5.4

Using a queue to store user-defined object

#include <iostream>
#include <queue>
#include <string>
using namespace std;
template <class T>
void print(T& c){
   for( typename T::iterator i = c.begin(); i != c.end(); i++ ){
      std::cout << *i << endl;
   }
}
class Vehicle{
   public:
   Vehicle( string description = "Unknown car",string license = "Unknown license", bool wax = false );
   string description() const;
   string license() const;
   bool wax() const;
   private:
   string description_, license_;
   bool wax_;
};
   inline
   Vehicle::Vehicle( string description, string license, bool wax )
      : description_( description ), license_( license ), wax_( wax )
   {} // empty
   string Vehicle::description() const
   {  return description_; }
   string Vehicle::license() const
   {  return license_; }
   bool Vehicle::wax() const
   {  return wax_; }
   int main( )
   {
      const char* description[] = { "A", "B","C", "D","E" };
      const char* license[] = { "a", "b", "c","d", "e" };
      const bool wax[] = { false, true, false, true, false };
      const int num_cars = sizeof( wax ) / sizeof( wax[0] );
      queue<Vehicle> line;
      int count = 0;
      while( count < num_cars || !line.empty() )
      {
         for( int i = 0; i < 2; ++i )
            if( count < num_cars )
            {
               cout << "A " << description[count] << ", license " << license[count] << ", is here for a wash";
               if( wax[count] )
                  cout << " and a wax";
               cout << endl << endl;
               line.push( Vehicle( description[count], license[count],wax[count] ) );
               ++count;
            }
            else
            break;
         cout << "ATTENTION PLEASE: a " << line.front().description()
         << ", license " << line.front().license()
         << ",\n\has been carefully washed ";
         if( line.front().wax() )
           cout << "and waxed ";
         cout << "and is available for pick-up\n\n";
         line.pop();
      }
}

Working with a Queue of Integers

#include <queue>
#include <iostream>
int main (){
    using namespace std;
    // A queue of integers
    queue <int> qIntegers;
    cout << "Inserting {10, 5, -1, 20} into the queue" << endl;
    // elements pushed into the queue are inserted at the end
    qIntegers.push (10);
    qIntegers.push (5);
    qIntegers.push (-1);
    qIntegers.push (20);
    // the elements in the queue now are {20, -1, 5, 10} in that order
    cout << "The queue contains " << qIntegers.size ();
    cout << " elements" << endl;
    cout << "Element at the front: " << qIntegers.front() << endl;
    cout << "Element at the back: " << qIntegers.back ();
    cout << endl << endl;
    cout << "Removing them one after another..." << endl;
    while (qIntegers.size () != 0)
    {
        cout << "Deleting element " << qIntegers.front () << endl;
        // Remove the element at the front of the queue
        qIntegers.pop ();
    }
    cout << endl;
    // Test if the queue is empty
    if (qIntegers.empty ())
        cout << "The queue is now empty!";
    return 0;
}