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Interactive
Other

Interactive Data Structure Visualizations: Binary Tree Traversals

For Students 9th - 10th
A great visualization / animation tool that illustrates the different traversal algorithms used with binary trees.
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Website
University of Auckland School of Computer Science

Morris: Trees

For Students 9th - 10th
A description of the binary tree data structure.
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Website
National Institute of Standards and Technology (NIST)

Dictionary of Algorithms and Data Structures: Binary Tree

For Students 9th - 10th
The DADS description of the binary tree abstract data structure.
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Article
Other

Free Codecamp: How to Think in Graphs

For Students 10th - 12th
In this article, we're going to demonstrate various applications of graph theory. These applications will contain detailed illustrations. As the author states, if you've been looking for a "graph theory and everything about it tutorial...
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Handout
Wikimedia

Wikipedia: Binary Tree

For Students 9th - 10th
A Wikipedia description of the binary tree abstract data type.