CustomCC0-1.0#cptp0021800
Unique Path Pair Query
Summary
- •Phase 4 / tree_queries, mo_on_tree
- •Reasoning-first competitive programming drill
Problem Description
Given a tree with n nodes, each node labeled with an integer, answer q queries of the form (u, v): How many distinct labels appear along the path from u to v?
How to read this problem in plain language:
- This is a Phase 4 reasoning drill focused on tre, m_tree.
- Typical lenses to test first: trees, queries, mo-algorithm.
- Constraints reminder: 1 ≤ n, , labels: 1 ≤
Mini examples for mental simulation:
1) Boundary example: Describe why this case is tricky. Explain expected behavior and why naive logic may fail.
2) Adversarial example: Adversarial case where naive greedy/local decision looks correct but fails globally.
Lite-mode writing target:
- Write 1~2 observations that shrink the search space.
- Name one final algorithm and state target complexity explicitly.
- Validate with at least 2 edge cases and one hand simulation.
Constraints
- •1 ≤ n, , labels: 1 ≤
Analysis
Key Insight
The goal is to force explicit intermediate reasoning before revealing more.
treesqueriesmo-algorithmoffline