skip list

(data structure)

Definition: A randomized variant of an ordered linked list with additional, parallel lists. Parallel lists at higher levels skip geometrically more items. Searching begins at the highest level, to quickly get to the right part of the list, then uses progressively lower level lists. A new item is added by randomly selecting a level, then inserting it in order in the lists for that and all lower levels. With enough levels, searching is O(log n).

Generalization (I am a kind of ...)
ordered linked list, insert is a Las Vegas algorithm.

Aggregate child (... is a part of or used in me.)
randomized algorithm.

See also jump list.

Note: A skip list may be seen as approximating binary search in a linked list.

Author: PEB


Code (C) at ePaperPress.

More information

(click on Dictionaries, then Skip Lists) diagrams and explanation (and code) at ePaperPress.

William Pugh, Concurrent Maintenance of Skip Lists, Tech. Report CS-TR-2222, Dept. of Computer Science, U. Maryland, April 1989.

Go to the Dictionary of Algorithms and Data Structures home page.

If you have suggestions, corrections, or comments, please get in touch with Paul Black.

Entry modified 19 August 2019.
HTML page formatted Mon Aug 19 08:55:22 2019.

Cite this as:
Paul E. Black, "skip list", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed. 19 August 2019. (accessed TODAY) Available from: