Implementing a priority queue that can be iterated over in C++

Question

I need to implement a priority queue for a project, but the STL\'s priority_queue is not indicated since we need to iterate over all elements and remove them random

Answer 1

I would follow the example set by some of the other container adapters in the standard library use composition and make the type of the underlying container a template parameter. Though since it is a school project that might be too much flexibility. You might start by using composition with one of the existing Containers and build from there if necessary.

Answer 2

STL's set should be usable to make what you want, although I must note that the list of requirements looks a little strange. You could just define a new type.

template<typename T, template<typename X> class impl_type = std::set> class prio_queue {
    typedef impl_type<T> set_type;
    typedef typename set_type::iterator iterator;
    // etc
public:
    // Forward the set's members
    T& top() {
        return *begin();
    }
    // etc
};

Answer 3

You should be able to implement your own priority queue using std::vector, std::make_heap, std::push_heap, and std::pop_heap. Isn't this how std::priority_queue is implemented? You'll just need to call std::make_heap again to fix the data structure when you remove a random element.

Do you need to iterate over the elements in order? There's a std::sort_heap algorithm to order the underlying std::vector.

Answer 4

Do you really need a priority queue ?

You need iterate over all items and remove randomly -> linked list

If you need to keep the list sorted, sort it at the beginning and then, when inserting new item, use insertion sort (insert new item on right place).