Simple example of Priority Queue

Here is a simple example of priority queue:

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy

//Example showing how simple priority queues work using C++

#include <iostream>

#include <string>

#include <vector>

#include <queue>



using namespace std;



class PrioritizedWord

{

private:

  int m_prio;

  string m_word;



public:

  explicit PrioritizedWord()

  { }

  explicit PrioritizedWord(const std::string& word, const int priority = 0):

                                   m_word(word), m_prio(priority)

  { }

  //Operator overloading for priority comparison

  const bool operator <(const PrioritizedWord& pW) const

  {

    return (m_prio < pW.m_prio);

  }

  //Operator overloading to print output

  friend ostream& operator <<(ostream& out, const PrioritizedWord& pW)

  {

    out<<pW.m_word;

    return out;

  }

  int getPrio(void)

  {return m_prio;}

  string getWord(void)

  {return m_word;}

};



int main()

{

  int somenum = 2;

  while(somenum > 0)

  {

    priority_queue<PrioritizedWord> wordQueue, zahidQueue, *temp=NULL;

    //Word Queue first time, Zahid Queue second time

    if(somenum%2==0)

    {

      temp = &wordQueue;

    }

    else

    {

      temp = &zahidQueue;

    }



    //Note the final order will not be the same as the specs do not

    //define behaviour in case two numbers with equal priority exist

    temp->push(PrioritizedWord("First", 23));

    temp->push(PrioritizedWord("Second", 23));

    temp->push(PrioritizedWord("Third", 23));

    temp->push(PrioritizedWord("Fourth", 51));

    temp->push(PrioritizedWord("Fifth", -1));



    cout<<"\n\nWord Queue elements (All elements lost):"<<endl;

    while(!wordQueue.empty())

    {

      cout<<wordQueue.top()<<" "<<endl;

      wordQueue.pop();

    }



    cout<<"\n\nZahid Queue elements (Elements preserved):"<<endl;

    if(!zahidQueue.empty())

    {

      priority_queue<PrioritizedWord>    tempQueue;

      while(!zahidQueue.empty())

      {

        PrioritizedWord &temppW = zahidQueue.top();

        cout<<temppW<<" "<<endl;

        tempQueue.push(PrioritizedWord(temppW.getWord(), temppW.getPrio()));

        zahidQueue.pop();

      }

      while(!tempQueue.empty())

      {

        PrioritizedWord &temppW = tempQueue.top();

        zahidQueue.push(PrioritizedWord(temppW.getWord(), temppW.getPrio()));

        tempQueue.pop();

      }

    }



    cout<<"\n\nZahid Queue - Removing an element and leaving the rest"<<endl;

    {

      priority_queue<PrioritizedWord>    tempQueue;

      while(!zahidQueue.empty())

      {

        PrioritizedWord &temppW = zahidQueue.top();



        if(temppW.getWord() != "Second")

        {

          tempQueue.push(PrioritizedWord(temppW.getWord(), temppW.getPrio()));

          zahidQueue.pop();

        }

        else

        {

          zahidQueue.pop();

          break;

        }

      }

      while(!tempQueue.empty())

      {

        PrioritizedWord &temppW = tempQueue.top();

        zahidQueue.push(PrioritizedWord(temppW.getWord(), temppW.getPrio()));

        tempQueue.pop();

      }

    }



    cout<<"\n\nZahid Queue elements after removal of element"<<endl;

    while(!zahidQueue.empty())

    {

      cout<<zahidQueue.top()<<" "<<endl;

      zahidQueue.pop();

    }

    somenum--;

  }



  return 0;

}

The output is as follows: