QuickSort on Doubly Linked List

Question

I want to implement the QuickSort Algorithm on a sync Doubly Linked List. I give the function \"partition\" the left and right border, then it starts to search lower values on t

Answer 1

Just from a quick skim, it seems that your list is not only doubly linked, but also is connected at the ends (so it's more like a Ring than like a list). In other words, if I were to iterate over your list (containing elements A, B, C, D), it wouldn't be:

A -> B -> C -> D -> stop

Instead it would be

A -> B -> C -> D -> A -> B -> C -> D -> A -> B ..... etc.

I suspect that could be why you are having an infinite loop.

I would create a reference to the last element of your list in your DoublyLinkedList class (example: in.last), use that for getting the last element, and have the first and last elements link to either null or some sort of NullListElement extends ListElement

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If you must keep it as a ring, I will still add a reference to the last element of your list, so that you can say something like:

if(walker == in.last) break; // stop