priority queue clear method

Question

How do I delete all elements from a priority queue? That means how do I destroy a priority queue? advanced thanks for your answer. Is there any clear- or erase-like method

Answer 1

priority_queue doesn't have a clear method. It may be that this is for interface simplicity, or because it there may be situations in which elements must be destroyed in priority-order, making a generic clear function unsafe.

Regardless, the following code block includes two functions to clear priority queues. The first works by building a temporary instance of a wrapper class around the priority_queue and then using this to access the underlying storage object, which is assumed to have a clear() method. The second works by replacing the existing priority_queue with a new queue.

I use templating so that the functions can be recycled time and again.

#include 
#include 
using namespace std;

template 
void clearpq(priority_queue& q) {
    struct HackedQueue : private priority_queue {
        static S& Container(priority_queue& q) {
            return q.*&HackedQueue::c;
        }
    };
    HackedQueue::Container(q).clear();
}

template 
void clearpq2(priority_queue& q){
    q=priority_queue();
}

int main(){
    priority_queue testq, testq2;

    //Load priority queue
    for(int i=0;i<10;++i)
        testq.push(i);

    testq2=testq;

    //Establish it is working
    cout<