NOTE
Skip List
Probabilistic ordered structure with multiple forward-pointer levels and expected logarithmic search/update.
This is a historical learning note and may contain outdated or incomplete understanding.
A skip list augments a sorted linked list with higher levels that skip over many elements. Randomized level assignment gives expected O(log n) search/insert/delete while preserving ordered/range traversal.
Its implementation is often simpler than a balanced tree and can work well in concurrent/storage systems, though it uses extra forward pointers and provides probabilistic rather than strict height bounds.
Redis sorted sets have historically used skip-list-style structures alongside hash lookup for ordered/range operations in relevant encodings.