CustomCC0-1.0#cp011-1182100
Tree Subset Connectivity
Summary
- •Phase 5 / trees, lca, dfs order
- •Reasoning-first competitive programming drill
Problem Description
Given a tree with n nodes, and q queries, each query selects a subset of nodes. For each query, determine if the induced subgraph is connected.
How to read this problem in plain language:
- This is a Phase 5 reasoning drill focused on trees, lca, dfs order.
- Typical lenses to test first: trees, connectivity, lca.
- Constraints reminder: 1 <= n, q <= 10^5, 1 <= k <= n, 1 <= u,v <= n, all queries together <= 2*10^5
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, q <= 10^5, 1 <= k <= n, 1 <= u,v <= n, all queries together <= 2*10^5
Analysis
Key Insight
The goal is to force explicit intermediate reasoning before revealing more.
treesconnectivitylca