Traversal is how we systematically visit every node in a binary tree exactly once. Because a tree has no single linear order built into it, we have to choose a rule for the order in which we touch the root and its two subtrees. The three classic depth-first rules are in-order (left, root, right), pre-order (root, left, right), and post-order (left, right, root). Each is a tiny variation on the same recursive idea, but each produces a very different output sequence.
Those differences matter in practice. In-order traversal on a binary search tree produces the keys in sorted order, which is why it is the go-to for printing or validating a BST and for finding an in-order successor during deletion. Pre-order is the natural choice for copying or serializing a tree, since the root is emitted before its children and can be rebuilt first. Post-order visits children before their parent, which is exactly what you want when freeing memory, deleting a tree, or computing values that depend on subtree results (like height or expression evaluation). You should also be comfortable with both the recursive version, which is short and mirrors the definition, and the iterative version, which makes the hidden call stack explicit.
As you watch, keep a small sample tree on paper and trace along with the speaker rather than just listening. Pay attention to the moment a node is actually "visited" (printed) versus merely passed through on the way down, since that single detail is what separates the three strategies. For the iterative videos, watch what gets pushed onto the stack and when, and ask yourself how that sequence reproduces the recursive behavior.
A broad introduction to traversing a binary tree that walks through all three depth-first strategies — in-order, pre-order, and post-order — in a single lesson. Based on the title and description, it explains the visiting order for each strategy and demonstrates the traversal on example trees so you can see how the output sequence differs.
This is the best starting point for the topic because it covers all three traversal orders together, making the contrast between them explicit; CodeWithHarry is a widely used programming-education channel known for step-by-step explanations aimed at beginners.
A focused, short treatment of in-order traversal that pairs a visualization of the node-visiting order with the corresponding code and a worked example. The emphasis is on seeing the recursion unfold visually rather than only reading the algorithm.
In-order is the traversal you will use most often with BSTs (sorted output, in-order successor), so a dedicated visual walkthrough is worth the four minutes; the animation directly supports tracing node sequences by hand.
An implementation-oriented video on performing post-order traversal iteratively — that is, without recursion — using an explicit stack. Expect a discussion of why post-order is the trickiest of the three to convert to an iterative form and a code walkthrough of the resulting algorithm.
It fills the recursive-versus-iterative subtopic with the hardest and most instructive case, and Dinesh Varyani's channel is known for detailed, animation-supported data structures and algorithms implementations.
Together these videos target MO2 most directly: the CodeWithHarry overview establishes all three visiting orders so you can predict node sequences, while the in-order visualization reinforces the traversal most tied to BST sorted output and to finding the in-order successor used in deletion (MO3). The iterative post-order video extends the same ideas into implementation detail — explicit stack management and code structure — which supports writing working traversal methods in your own BST class (MO5). Watching all three also sharpens your sense of tree shape, subtree relationships, and root-to-leaf structure that underpins MO1.
These videos were chosen from YouTube on October 2, 2026. Each has captions; the player turns them on. Videos on YouTube can be changed or removed — if one no longer plays, tell your instructor. If a player does not appear, use its Watch on YouTube link.