列出优先级队列

Question

I have a college programming project in C++ divided into two parts. I beggining the second part where it's supposed to use priority_queues , hash tables and BST 's.

I'm having trouble (at least) with priority queues since it's obligating myself to redone a lot of code already implemented in the first part.

The project it's about implementing a simple airport management system and, therefore, I have classes like Airport (main class), Airplane, Terminal and Flight. My airport had a list of terminals but now the project specification points out that I must keep the terminals in a priority_queue where the top contains the terminal less occupied, ie has less flights.

For each class, I have CRUD functions but now how am I supposed, for example, edit a terminal and add a flight to it? With a list, I just had to iterate to a specific position but now I only have access to object in the top of the queue. The solution I thought about was to copy the priority queue terminals to a temporary list but, honestly, I don't like this approach.

What should I do?

Thanks in advance.

Answer 1

It sounds like you need a priority queue with efficient increase and decrease key operations. You might be better of creating you own your own priority queue implementation.

The priority_queue container is great for dynamic sets. But since the number of terminal in an airport are pretty much fixed you can a fixed size container with the heap family of algorithms.

As the internal storage, you could use any container that provides random access iterators (vector, array, deque). Then, use make_heap(), sort_heap() family of functions to heapify the array. Now you can cheaply access the top(), modify the priority of a random member in the heap and iterate through all elements easily.

For an example see: http://www.cplusplus.com/reference/algorithm/make_heap/