(data structure)

**Definition:**
A theoretical data structure for n items. It starts with a *balanced binary search tree* of about √(n) nodes. The *leaf* nodes lead to "tentacles" or *linked lists*, each of about √(n) nodes.

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

*balanced binary search tree*, *linked list*.

*Note:
It is described to prove a theorem, not as a useful data structure. *

Synder says the tentacles may be ordered, unordered, or semi-ordered. For faster access to the end of the tentacle for updates, there can be links from the beginning (*head*) to the end (*tail*).

* This note gives more details to justify the counts above. The body consists of about √(n) nodes, of which about √(n)/2 would otherwise be considered leaf nodes. Since each node has two subtrees, there are about 2 × √(n)/2 = √(n) tentacles. Therefore each tentacle has about (n - √(n)) / √(n) = √(n)-1 nodes.*

Author: PEB

**Lawrence Snyder**, *On Uniquely Represented Data Structures*, Proc. 18th Annual Symposium on Foundations of Computer Science (FOCS), pp 142-146, 1977.

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Entry modified 29 August 2014.

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Paul E. Black, "jelly-fish", in
*Dictionary of Algorithms and Data Structures* [online], Paul E. Black, ed. 29 August 2014. (accessed TODAY)
Available from: https://www.nist.gov/dads/HTML/jellyfish.html