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USACO · 2025 · US Open · platinum-3

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trees · data-structures

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sample trace

Package Pickup: trees walkthrough

Package Pickup: use the linked editorial?s trees, data structures idea on the published sample, then verify the displayed output.

Published input100 3 7 10 10 20 20 30 30 7 7 11 11 13 13 17 17 24 24 26 26 33 33 2 1 1 1 5 2 6modelAlgorithm ideaUse the rooted tree structure: each subtree is a self-contained region, and parent/child summaries support the requested query.task resultExpected output22 3
  1. 1

    Root

    Choose the root and record parent, child, and subtree relationships.
  2. 2

    Combine

    Process child subtrees or ancestor paths using the task?s required summary.
  3. 3

    Answer

    Translate the relevant tree region into the requested value or output.
  4. 4

    Verify the sample

    Use the published sample output to check the result of this idea on the displayed input.
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