Question

I’m having trouble finding the right C# data structure. I’m looking for a PriorityList. It needs to have the following:

• Only one item a given priority
• Must remain sorted at all times
• Ability to add an item to the end of the list — prorityList.Add(item)
• Ability to insert an item at a given priority — priorityList.Add(3, item)
• Ability to access any element using the priority — priorityList[3]
• Ability to remove an item at a given priority — priorityList.RemoveAt(3)
• When an item is added or removed, the rest of the list must shift up or down appropriately — for example, if the third item is removed, the fourth item becomes the third item, the fifth item becomes the fourth item, etc.

C#’s SortedList looked promising, but it can’t handle inserting at a priority that already exists or removing an element at a given priority (having the list shift appropriately in both cases).

Answer 1

If you just use a standard List<T> that should give you everything you have asked for if you use priority == index.