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Teaching Binary Trees
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We all love to be creative in our class presentations, especially when we are sure that the topic being presented is new to the majority of our students. "Binary trees" is often one of those topics. In addition to the ideas that our colleagues present, there are many links that provide animations of binary trees.
Teaching Binary Trees
Contributed by Leigh Ann Sudol
Fox Lane High School
Bedford, New York
Objective: To provide students with a visual representation of the creation of a binary tree, to traverse the tree visually, and to add nodes to a tree.
Materials: Students will need a small stack of Post-it® brand notes (you can divide a regular stack between 5 or 6 groups easily) and a space to work (tables, wall, chalkboard, etc.).
Procedure: Divide the class into groups of two students. Each group is to play the following game:
One student is to think of two things (dog/cat, house/barn, etc.) and a question that answers as yes for one of the objects and no for the other. (For example, for dog and cat: Does it bark? yes=dog, no=cat)
The other student thinks of a person or thing (does not have to be one of the items, but can be). The first student is to use the question tree to try and guess the item that the second person is thinking of. If the player reaches a leaf note and it is not his item he or she is to give a question that would be yes for one item but no for another item. At that point the Post-it notes are rearranged, inserting the new item, and the game is played again.
Once students have played the game enough to be comfortable with it they write directions for how to build the Post-it note tree as well as how to search for a correct answer to someone else's guess.
The Post-it notes provide a visual representation of the question tree. Students are usually able to write the code for a program after playing the game. The game also provides an excellent resource for tracing problematic code. Post-it notes can also be used for tracing other dynamic data structures, such as linked lists.
Useful Tree Links
Contributed Anonymously
Visualization helps many students understand difficult concepts. One method of visualizing tree operations is to actually watch these operations in action! The following Web links provide animations or applications involving trees. Enjoy!
Binary Tree
This very simple binary tree animation allows you to insert and delete nodes with integer values and search for a specific integer value in the tree.
 Binary Tree
Binary Tree Traversals
Watch your favorite traversal through a binary tree OR test yourself on the different binary tree traversals.
Binary Tree Traversals
Heaps
In this animation, both the array representation (used in the implementation of the algorithm) and the (logical) tree representation are shown. This is to demonstrate how the tree is restructured to make a heap again after every insertion or deletion.
Heaps
Contribute
If you would like to contribute other suggestions for teaching binary trees, please submit your ideas.
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