Meaning of Algorithms in Pdf

Finding a subset of a list such that every item in the subset appears in exactly two other subsets

Let’s say I have a List of items that consists of five items.
I want to create two lists, L1 and L2, containing the subset of this list that shares elements with only each other (i.e. containing only one item from the original list).
It is clear that the algorithm I want to write is probably in some kind of recursion, but I can’t for the life of me figure out how to approach the problem. Any tips or ideas?
Any help greatly appreciated.
Edit: Clarification:
I want to find a subset of the list that all shares elements with all the other subsets, i.e.:
List of elements: 2, 1, 3, 4, 2
L1 contains: 2, 1
L2 contains: 1, 2, 3, 4

I want to take as many elements as I want to from the original list to create a list of lists, and the subsets in these lists all contain only elements that appear in two other lists.
It looks like this sort of question might be relevant to my problem, but I don’t really know how to translate the title into a question.

A:

The same sort of problem might be addressed using a tree data structure. You could, for instance, maintain an AVL tree (binary search tree): this would store the partial lists of the items as nodes, and link the nodes together to form the complete list. … Read the rest