PriorityQueue in C#

With the arrival of .NET 6, we have a new collection type, the PriorityQueue (priority queues). In this post, we’ll see how to work with it. 

1 - What is PriorityQueue in C#?

Previously, we saw the Queue<T> type, which represents a FIFO queue. 

The PriorityQueue type allows us to specify the position in which we want to insert each element we want to add. This new type is represented as PriorityQueue<TElement, TPriority>(); the first generic type will contain our value, and the second one defines the priority.

Using PriorityQueue can feel quite similar to using a SortedList, but they are not the same, because queues aren’t intended to be used as lists , even though it’s technically possible.

2 - Creating a PriorityQueue and adding elements in C#

To create a priority queue (PriorityQueue), we just need to instantiate it and call the .Enqueue() method to insert elements. Remember, we must pass two parameters: the value and the priority.

PriorityQueue<string, int> colaPrioridad = new PriorityQueue<string, int>();

colaPrioridad.Enqueue("Opel", 2);
colaPrioridad.Enqueue("Audi", 1);
colaPrioridad.Enqueue("BMW", 3);

• Note: if you add multiple elements with the same priority, they’ll be dequeued in reverse order

3 - Receiving elements from a PriorityQueue in C#

To retrieve elements, we have three options

• Peek(): This returns the next item in the queue without removing it.
• Dequeue(): This returns the next item and also removes it from the queue.
• EnqueueDequeue(): Alternatively, you can use this, which lets you both retrieve an item from the queue and insert a new one at the same time.

string resultPeek = colaPrioridad.Peek();
string resultDequeue = colaPrioridad.Dequeue();
string resultDequeue2 = colaPrioridad.EnqueueDequeue("Mazda", 3);
Console.WriteLine(resultPeek); //Audi
Console.WriteLine(resultDequeue); //Audi again
Console.WriteLine(resultDequeue2); //Opel

4 - Removing elements from a priority queue in C#

To remove elements from a priority queue without retrieving them, the only option is to clear the queue using .Clear().

colaPrioridad.Clear();

Conclusion

In this post, we’ve seen how to create a priority queue in C#

How to add elements to a priority queue

How to retrieve elements from a priority queue.