DFS follows a branch
Recursion or a stack carries state from parent to child.
Trees and BST
6 chapters · 15 challenges · The Whisper Woods
Understand the idea, practise through play, then prove it in code. Choose your next quest below.
Visual introduction to this topic
Start here · 3 minute mental model
What is a tree?
A tree organizes nodes into parent-child branches with one path from the root to each node. Its shape lets algorithms solve a whole structure by solving its subtrees.
Think of a game skill tree. Unlocking one skill opens only its descendants. You can explore one branch deeply or visit every skill at the same depth.
Carry the parent rule downward and combine child answers upward.
BFS follows a level
A queue visits every node at one depth before the next.
BST adds an invariant
Every left value is smaller and every right value is larger under the chosen rule.
What you will learn firstThe Inorder Path
Begin the guided lesson Visit left, node, then right
01
DFS Traversals
0/2 completePractice DFS traversals through 2 visual expeditions.
02
BFS Levels
0/3 completePractice BFS levels through 3 visual expeditions.
03
BST Invariants
0/3 completePractice BST invariants through 3 visual expeditions.
04
Path State
0/3 completePractice path state through 3 visual expeditions.
05
Construction
0/2 completePractice construction through 2 visual expeditions.
06
Lowest Ancestor
0/2 completePractice lowest ancestor through 2 visual expeditions.
Source reviewed
Built from authoritative material
This track is checked against the sources below. Visual traces still carry their own complete or guided coverage label, so unfinished explanations are not presented as complete executions.