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Why Did the Cow Cross the Road

USACO · 2017 · February · platinum-1

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trees

The organizer’s problem statement is available at the official source link.

sample trace

Why Did the Cow Cross the Road: trees walkthrough

Why Did the Cow Cross the Road: use the linked editorial?s trees idea on the published sample, then verify the displayed output.

Published input5 5 4 1 3 2 1 3 2 5 4modelAlgorithm ideaUse the rooted tree structure: each subtree is a self-contained region, and parent/child summaries support the requested query.task resultExpected output0
  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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