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    <p>I had the same problem, where I wanted to iterate over a priority queue without dequeuing (hence destroying my queue). I made it work for me by recasting my priority_queue pointer to a pointer to a vector (as my <code>priority_queue</code> uses vector as its container). Here is how it looks like:</p> <pre><code>class PriorityQueue { private: class Element { int x; //Other fields ... .. //Comparator function bool operator()(const Element* e1, const Element* e2) const { // Smallest deadline value has highest priority. return e1-&gt;x &gt; e2-&gt;x; } }; // Lock to make sure no other thread/function is modifying the queue // Ofcourse we can do our operation w/o lock. if we are sure what is happening in other functions pthread_mutex_t lock; std::priority_queue&lt;Element*, std::vector&lt;Element*&gt;, Element&gt; pq; public: PriorityQueue(); ~PriorityQueue(); //print the all the elements of the queue void print_queue_elements() { std::vector&lt;PriorityQueue::Element*&gt; *queue_vector; //Acquire the lock pthread_mutex_lock(&amp;lock); //recast the priority queue to vector queue_vector = reinterpret_cast&lt;std::vector&lt;PriorityQueue::Element*&gt; *&gt;(&amp;pq); for(std::vector&lt;PriorityQueue::Element*&gt;::iterator it = (*queue_vector).begin(); it != (*queue_vector).end(); it++) { //Assuming Element class has string function printf("My Element %s", (*it)-&gt;string); //other processing with queue elements } //Release the lock pthread_mutex_unlock(&amp;lock); } //other functions possibly modifying the priority queue ... .. . }; </code></pre> <p>Now since I am using reinterpret_cast, people can argue about type-safety. But in this case I am sure about all other functions accessing/changing the queue (all of which are safe).. and I feel this is a much better way than copying the content of whole queue to some other container.</p> <p>I was actually expecting <code>static_cast</code> to work.. as priority_queue is adaptor over container (vector in our case), but it doesnt and I had to use <code>reinterpret_cast</code>.</p>
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    1. POHow to iterate over a priority_queue?
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    1. USakshay singh
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