How to clear q priority_queue object in the STL programming?

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Hello everyone, I'd like to clear a priority_queue object ,but it doesn't has the "clear" member function.
I'd rather not to pop all the members of the queue one by one because it may cost lots of time.
What can I do with it?

P.S.
My English is poor, I hope it I had described it clearly enough. Thanks a lot.

Posted 27-Jul-10 2:33am

LieDragon

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Sauro Viti · Accepted Answer · 2010-07-27T02:49:00

You can declare your own class this way:

C++

template <class Type>
class my_priority_queue
{
private:
   std::priority_queue<Type>* m_pQueue;

public:
   my_priority_queue()
   {
      m_pQueue = new std::priority_queue<Type>;
   }

   ~my_priority_queue()
   {
      delete m_pQueue;
   }

   bool empty() const
   {
      return m_pQueue->empty();
   }

   void pop()
   {
      m_pQueue->pop();
   }

   void push(const Type& _Val)
   {
      m_pQueue->push(_Val);
   }

   std::priority_queue<Type>::size_type size() const
   {
      return m_pQueue->size();
   }

   std::priority_queue<Type>::value_type& top() const
   {
      return m_pQueue->top();
   }

   void clear()
   {
      delete m_pQueue;
      m_pQueue = new std::priority_queue<Type>;
   }
};

Aescleal · Accepted Answer · 2010-07-27T04:10:00

Simple answer is don't clear it!

priority_queues are designed to have stuff inserted in and sorted in priority order. They not designed to have stuff removed from them, well, except by yanking stuff off the front. If you want to clear it then bin the object and start again:

q = std::priority_queue<int>();</int>

Failing that you could always just repeatedly pop stuff off the queue unitl it's empty:

while( !q.empty() ) q.pop();

For me the first way is a lot cleaner but YMMV.

Cheers,

Ash

PS: I wouldn't worry about the costs of the second method. There's no reason why you can't implement pop to take hardly any time at all, just enough to destruct the element.

How to clear q priority_queue object in the STL programming?

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