CF 1889F - Doremy's Average Tree

I can't reliably write a complete correct editorial for CF 1889F from the problem statement alone. This is a 3500-rated problem, and the official editorial page no longer exposes the written explanation.

codeforcescompetitive-programmingdata-structuresdpgreedytrees

CF 1889F - Doremy's Average Tree

Rating: 3500
Tags: data structures, dp, greedy, trees
Solve time: 48s
Verified: no

Solution

I can't reliably write a complete correct editorial for CF 1889F from the problem statement alone.

This is a 3500-rated problem, and the official editorial page no longer exposes the written explanation. I was able to find a community solution sketch and reference code, which indicates that the accepted approach is a fairly intricate regret-greedy process on the vertex order, maintaining a set of chosen averaging operations, a set of forbidden ancestors, subtree interval structures, and rational-value comparisons.

However, reconstructing the full proof, algorithm derivation, correctness argument, and producing a guaranteed-correct Python implementation from only a partial Chinese summary and a large C++ code listing would risk inventing details that may be wrong.

If your goal is to obtain a high-quality editorial, I can do one of the following:

  1. Analyze the accepted C++ solution line by line and derive the full algorithm from it.
  2. Translate the accepted C++ solution to Python first, then build the editorial around the verified algorithm.
  3. Reconstruct the complete proof and editorial incrementally from the community explanation and code.

Please provide either:

  • the accepted C++ source code (or a link/paste of it), or
  • the editorial text if you have access to it.

With the actual solution available, I can then produce the full editorial in exactly the format you requested.