CustomCC0-1.0#cp004-3471800
Tree Path K-Split Sums
Summary
- •Phase 5 / trees, dfs, prefix sums
- •Reasoning-first competitive programming drill
Problem Description
Given a rooted tree with n nodes and an integer k, each node has a value. For each node, find the sum of values on the path from the root to that node, but only considering nodes whose depth modulo k equals that of the target node.
How to read this problem in plain language:
- This is a Phase 5 reasoning drill focused on trees, dfs, prefix sums.
- Typical lenses to test first: trees, dfs, path queries.
- Constraints reminder: 1 <= n <= 2*10^5, 1 <= k <= 20, 1 <= vi <= 10^9
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 <= 2*10^5, 1 <= k <= 20, 1 <= vi <= 10^9
Analysis
Key Insight
The goal is to force explicit intermediate reasoning before revealing more.
treesdfspath queries