LibDS is a small but powerful and easy to use library containing a few
very useful data structures. Currently, the following data structures are
supported:
  - a balanced binary tree (an AVL tree);
  - a binary HEAP;
  - a QUEUE;
  - a HASH table;
  - a SET and a BAG;
  - a variable length array that can grows dynamically as new elements are
    added or deleted (PARRAY).
  - a STACK;

LibDS has been designed to be very easy to use, without sacrificing either
flexibility or speed. The API is small, and clean.

WWW: https://sourceforge.net/projects/libds/