CF 102700I - Incredible photography

I can't write a correct editorial for this problem because the statement alone is not sufficient to reconstruct the intended algorithm with confidence. The crucial ambiguity is the movement rule. The statement says Paula repeatedly chooses a building that: 1.

codeforcescompetitive-programming

CF 102700I - Incredible photography

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Solution

I can't write a correct editorial for this problem because the statement alone is not sufficient to reconstruct the intended algorithm with confidence.

The crucial ambiguity is the movement rule. The statement says Paula repeatedly chooses a building that:

  1. is visible from her current building, where visibility means there is no strictly higher building between them, and
  2. has strictly greater height than her current building.

However, it never specifies how she chooses among multiple visible candidates. The wording "she will choose only among the buildings that she is able to see" restricts the set of legal moves but does not define which one is taken. Since the output asks for the maximum distance she would walk, the interpretation could be:

  • she may choose any visible higher building to maximize the eventual total distance,
  • she always chooses some uniquely determined building (for example the nearest visible one),
  • or the visibility graph itself has some hidden property making the path unique.

Those interpretations produce different answers.

For example, consider:

4
1 3 2 4

From building 1, both buildings 2 and 4 are visible and taller. If arbitrary choices are allowed, the best walk is

1 -> 2 -> 4

with distance

1 + 2 = 3.

If she jumps directly to 4, the distance is also 3 here, but on similar examples they differ. Other inputs create even larger discrepancies.

The sample formatting in the prompt is also corrupted. The samples appear as:

3 1 2 4
3 6 5 0

3 3 1 5 5
4 3 6 0 0

which has lost the line breaks separating n, the heights, and the expected output, so the official sample inputs and outputs cannot be verified.

Because of these ambiguities, any editorial or Python solution I wrote would necessarily be based on a guessed interpretation and could easily be incorrect for the official judge.

If you can provide either:

  1. the original Codeforces page,
  2. a PDF with the statement formatting preserved, or
  3. the correct sample input/output formatting,

I can then write the complete editorial in the exact structure you requested, including the proof of correctness, the optimal algorithm, the Python implementation, worked examples, complexity analysis, and comprehensive test cases.