The finale ties every piece together - build a set from a fixed seed, delete a couple of keys, and assert the exact ordered contents, a search path, a range, and a select-by-rank all at once. Insert, delete, search, iterate, and index all prove themselves in one scenario.
Build a list from a seed and a known insert-then-delete sequence and assert its exact contents, path, range, and indexed queries.
This is the promise the project was built to keep: a genuine ordered map backed by
a skip list, and every layer proving itself in one scenario. From seed 1 the eight
inserts build a known structure with height-3 towers at 1, 4, and 5; deleting 7 and 2
unlinks two nodes and fixes every span behind them; and then the whole public surface
agrees on the result. Keys reads the six survivors in order off level 0, Range
jumps to 3 and walks to just before 9, and Path shows search hopping through the
express lanes 1, 4, 5 to reach 8 in three steps instead of scanning.
The indexed queries close the loop: Rank(8) is 4 because four keys precede it, and
Select(3) returns 5 because it sits at index 3 - answers only correct if insert and
delete kept every span exact through all ten mutations. From a node with a tower of
pointers, you have built a deterministic ordered set that searches, inserts, deletes,
iterates, ranges, and indexes by position in expected O(log n) - the same
probabilistic, rotation-free design that powers Redis sorted sets and countless
ordered indexes, minus the production trimmings. That is a real skip list, and it is
yours.
s := NewSkipList(1)for _, k := range []int{3, 7, 1, 9, 5, 2, 8, 4} { s.Insert(k, k*10) }s.Delete(7); s.Delete(2)// Keys()==[1 3 4 5 8 9]; Range(3,9)==[3 4 5 8]; Path(8)==[1 4 5]// Search(8)==(80,true); Rank(8)==(4,true); Select(3)==(5,true)