Tree is a project mainly written in C, it's free.
tree struct
LINK TREE STRUCT
LICENSE: All source codes are provided under the terms of GNU GPL license, version 2
WARNING: Some of the source codes may contains errors, and may lead to different results on different kind of machines
tree_define.h - definations of data types; tree.h - definations of struct Tree and its operations; tree_node.h - definations of struct tree_node and its operations;
tree_operation.h - functions for producing function implementations for struct Tree and tree_node; tree_base.h - default implementations for tree operations; tree_node_base.h - default implementations for tree node operations;