IBM Watson Challenge project for CSSE 413 - AI
Included code for AVL tree found on GitHub that was open source, written by Pavel Grafov, and available at: https://github.com/pgrafov/python-avl-tree
The file pyavltree.py, and all code included is the intellectual property of Pavel Grafov, readme below
Copyright (c) 2010 Pavel Grafov
Implementation of AVL trees (http://en.wikipedia.org/wiki/AVL_tree) in Python. Class AVL Tree supports the following functionality:
- insertion of a new entry in the tree;
- removal of any entry in the tree;
- search for any entry in the tree;
- "sanity check" for the tree (described later);
- 4 various tree traversals
- preorder,
- inorder,
- postorder,
- inorder non-recursive.
I would like to mention some sources, that helped me a lot while working on this code:
- Wikipedia 1a) http://en.wikipedia.org/wiki/AVL_tree Description of AVL trees. 1b) http://en.wikipedia.org/wiki/Tree_traversal Description of tree traversals in binary search trees and sample implementations of traversal algorithms in pseudocode.
- http://www.cse.ohio-state.edu/~sgomori/570/avlrotations.html Rotation algorithms for putting an out-of-balance AVL tree back in balance.
- http://sourceforge.net/projects/standardavl/ Implementation of AVL trees in C++. I borrowed an idea of "sanity check" - a method, which traverses the tree and checks that tree is in balance, contains no circular references, height for each node is calculated correctly and so on.
- http://oopweb.com/Algorithms/Documents/AvlTrees/Volume/AvlTrees.htm From this page I borrowed the idea how to correctly delete an entry from an AVL tree.
This code is available under MIT License.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.