How do I reserve capacity and shrink-to-fit with std::queue?

In C++, the `std::queue` container does not provide direct methods to reserve capacity or shrink-to-fit because it is an adapter that uses a deque or list as its underlying container. However, we can manage the underlying container to achieve similar behavior indirectly.

Reserving Capacity in std::queue

Since `std::queue` does not directly support reservation, we can create an underlying container (like `std::deque`) and reserve capacity on that container before assigning it to the queue.

Shrinking to Fit in std::queue

To reduce the capacity of the underlying container, you need to clear the queue and then create a new queue with a new underlying container that has been shrunk. Clearing the queue effectively removes elements, and you can then recreate it with the desired size.

Example of Using std::queue with Capacity Management

#include <iostream>
#include <queue>

int main() {
    std::deque tempDeque;
    tempDeque.resize(100); // Reserve capacity using deque

    std::queue> myQueue(std::move(tempDeque));

    // Adding elements
    for(int i = 0; i < 10; ++i) {
        myQueue.push(i);
    }

    // Shrinking the queue
    std::queue> newQueue;
    while (!myQueue.empty()) {
        newQueue.push(myQueue.front());
        myQueue.pop();
    }

    std::cout << "New Queue Size: " << newQueue.size() << std::endl;

    return 0;
}