Invalid testcase(s) for Problem-B from 2022-2023 ICPC, NERC, (Unrated, Online Mirror)

Revision en1, by The5threich, 2024-02-07 18:09:05

I recently encountered Problem-B BinCoin from 2022-2023 ICPC, NERC, Northern Eurasia Onsite (Unrated, Online Mirror, ICPC Rules, Teams Preferred) while practicing random 2200 problems.

The problem is based on a binary rooted tree generated by the jury, and a random in-order traversal of that tree. I was sure my solution to this problem was reliable. But it seemed to RTE on test-16. I tried several methods to circumvent the situation to no avail.

Today I attempted to stress test my solution by generating random binary rooted trees, with random traversals.
While validating I mistakenly entered an even number for the number of nodes and realized it immediately.
I couldn't find any valid test case which would reliably thwart my approach.
So I went ahead and put an assertion for the input to see if the input is incorrect by RTE.
To my surprise the system AC's my solution!

Tags bug report, fail in test case

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  Rev. Lang. By When Δ Comment
en5 English The5threich 2024-02-10 18:37:44 217
en4 English The5threich 2024-02-08 16:30:48 6
en3 English The5threich 2024-02-07 20:07:54 8 (published)
en2 English The5threich 2024-02-07 19:59:12 3604 Tiny change: 'proach">\n...\nLet $a$,' -> 'proach">\nLet $a$,'
en1 English The5threich 2024-02-07 18:09:05 1052 Initial revision (saved to drafts)