Expression Arbor — Interactive Expression Tree & Traversal Practice

Author / Site: Course instructional team (self-contained interactive HTML activity)

Summary: Expression Arbor is a browser-based interactive exercise in which students build a binary expression tree from a given arithmetic expression by placing operator and operand tiles onto a growing tree structure. As the tree takes shape, the activity displays the resulting pre-order, in-order, and post-order 'walks' and scores each attempt against the correct traversal sequences. Color coding distinguishes operators, numbers, and parentheses, and a round map tracks progress, correctness, and points across multiple expression challenges.

Relevance to Module: The activity puts the module's core vocabulary into play: students must reason about root, parent-child relationships, subtrees, leaves, and depth while constructing each tree. Because expression trees make the three depth-first traversal orders produce visibly different and meaningful outputs (prefix, infix, postfix notation), the resource directly reinforces the traversal content at the heart of this lesson and gives students a concrete reason why traversal order matters.