How to Implement Priority Queue Using Multimap in C++?

// C++ program to implement a priority queue using a
// multimap
#include <iostream>
#include <map>

using namespace std;

template <typename T, typename Priority>
class PriorityQueue {
private:
    multimap<Priority, T> elements;

public:
    // Method to push an element with its priority to the
    // priority queue
    void push(const T& element, const Priority& priority)
    {
        elements.emplace(priority, element);
    }

    // Method to pop the element with the highest priority
    // from the priority queue
    T pop()
    {
        if (elements.empty()) {
            throw out_of_range("Priority queue is empty");
        }
        auto highestPriority = elements.begin();
        T element = highestPriority->second;
        elements.erase(highestPriority);
        return element;
    }

    // Method to peek at the element with the highest
    // priority without removing it
    T peek() const
    {
        if (elements.empty()) {
            throw out_of_range("Priority queue is empty");
        }
        return elements.begin()->second;
    }

    // Method to check if the priority queue is empty
    bool empty() const { return elements.empty(); }
};

int main()
{
    // Create a priority queue of strings with integers as
    // priorities
    PriorityQueue<string, int> pq;
    pq.push("Task 1", 3);
    pq.push("Task 2", 1);
    pq.push("Task 3", 2);
    pq.push("Task 4", 4);

    // Peek at the task with the highest priority
    cout << "Peeked task: " << pq.peek() << endl;

    // Pop and print tasks until the priority queue is empty
    while (!pq.empty()) {
        cout << pq.pop() << endl;
    }

    return 0;
}