What are the lesser known but useful data structures?

Abstraction: Crowd-sourced catalog of obscure but practically valuable data structures

Key points:

• Community question on Stack Overflow asking for under-appreciated data structures beyond linked lists, binary trees, and hash tables
• Explicitly calls out skip lists and Bloom filters as examples of what is being sought
• Also interested in clever algorithmic techniques like Dancing Links (exploiting doubly-linked list pointer manipulation for exact-cover problems)
• One answer per data structure format to allow community voting to surface the most useful
• Framed as enriching a programmer's toolbox with structures that rely on interesting underlying ideas

Connections: Stackoverflow · Data Structures · Skip Lists · Bloom Filters

Source: http://stackoverflow.com/questions/500607/what-are-the-lesser-known-but-useful-data-structures?rq=1