C++ priority_queue Definition Explained

In C++, the priority_queue is a container adapter that provides a way to access elements based on priority. It can be used to store a group of elements and sort them according to priority. The priority_queue class template is located in the header file and provides the following definition:

template <class T, class Container = vector<T>, class Compare = less<typename Container::value_type>>
class priority_queue;

Among them, T is the type of elements stored in the priority_queue, Container is the type of container used to store elements, defaulting to vector, and Compare is the predicate used to define element priority comparison, defaulting to std::less.

The default sorting method of priority_queue is to arrange elements in either descending (by default) or ascending order based on the comparison Comparator’s requirements. This implies that in the default setting, the top element of the priority_queue is the largest element.

The priority_queue class provides the following commonly used member functions:

1. Insert element x into the priority_queue.
2. Remove the top element with pop().
3. top(): returns a reference to the top element.
4. empty(): check if the priority queue is empty.
5. size(): Returns the number of elements in the priority queue.

It is important to note that the priority_queue does not provide iterators, so it is not possible to directly access the elements in the container. If you need to iterate through the elements, you can continuously use the pop() function to retrieve the top element one by one.