Problem context and objectives
Mission briefing
Archive pathfinder · Clues branch through a living archive
Explore only the branches that can still contain the answer: The Target Root Path.
Ignoring the parent-child rule turns a focused search into a full maze traversal.
How you win
- 1Recognize when Root-to-leaf path sum matches the clues
- 2Keep this true after every move: remaining equals target minus every value on the active root-to-current path
- 3Reach the result within O(n) time and O(height) space
Rules and pressure
- Target cost: O(n) time and O(height) space
- State rule: remaining equals target minus every value on the active root-to-current path
Lesson 1 of 3
Build a connected root-to-leaf route and track its branch-local remainder. Zero remaining succeeds only at a leaf.
Build a connected root-to-leaf path that spends the target charge exactly.
Your call · Which path reaches target 22?