Quicksort on doubly linked list

Quicksort is a popular sorting algorithm that can be used to sort elements in an array or a singly linked list. When it comes to a doubly linked list, the process is a bit different.

In a doubly linked list, each node has pointers to both the next and the previous node in the list. Quicksort on a doubly linked list is a sorting algorithm that uses the same divide-and-conquer strategy as Quicksort on an array. However, instead of partitioning the list into two sublists based on a pivot element, the algorithm partitions the list into three sublists based on a pivot node.

The algorithm works by selecting a pivot node from the list, usually the last node in the sublist. It then partitions the list into three sublists:

1. A sublist of nodes with values less than the pivot value.
2. A sublist of nodes with values equal to the pivot value.
3. A sublist of nodes with values greater than the pivot value.

The algorithm then recursively applies the same process to the first and third sublists until the entire list is sorted.

During the partitioning process, the algorithm needs to update the next and previous pointers of the nodes to correctly link the sublists. This can be a bit more complex than in an array or a singly linked list, but it can be achieved with careful bookkeeping of the node pointers.