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Обсуждение задачи 2181. Студент, или Туда и обратно🦄imosk72🦄[GTGU] Strange statement // Задача 2181. Студент, или Туда и обратно 9 мар 2025 16:50 > The student’s home is located at the coordinates (1, 1), and the university is at the coordinates (N, M). It means, for example, if N == 1 && M == 1 then university have same coordinates as home. Of course we can not use any roads in such case. But according to the sentence: > There are a total of N streets running from north to south and M streets running from west to east. there are some roads that can not be used. I think there should be N - 1 streets running from north to south and M - 1 streets running from west to east. andreyDagger`~ Wrong tests? [5] // Задача 2181. Студент, или Туда и обратно 19 янв 2025 20:37 It seems like in test 7 n=300, m=300, k=0. Answer is obviously 709227659, but it gives WA. Oleg Vasilenko (Chelyabinsk) Re: Wrong tests? [2] // Задача 2181. Студент, или Туда и обратно 20 янв 2025 21:45 I also got answer 709227659 to this testcase. Yes, seems like incorrect tests or incorrect problem statement. Admins, please look at this issue. At least please check test 7. Also please, clarify order of N and M values in input data (if they go in M,N order then correct statement please). P.S. Also the problem is not so difficult as described in post-contest jury solutions. If problem statement is correct, it has got simple O(N*M) dp solution (based on https://en.wikipedia.org/wiki/Lindstr%C3%B6m%E2%80%93Gessel%E2%80%93Viennot_lemma principle). andreyDagger`~ Re: Wrong tests? [1] // Задача 2181. Студент, или Туда и обратно 21 янв 2025 02:51 Yeah, jury solution is complicated. Mine solution is a bit different, but still straightforward O(N*M*(N+M)) dp, with simple O(1) transitions from each state Oleg Vasilenko (Chelyabinsk) Re: Wrong tests? // Задача 2181. Студент, или Туда и обратно 26 янв 2025 09:18 Admins, any decision about this problem? Is test 7 correct? 🎧 Vadim Barinov \Frez_Fstilus/'``' :) Re: Wrong tests? [1] // Задача 2181. Студент, или Туда и обратно 28 янв 2025 02:05 We fixed wrong tests. Original author miswrote 10^9+7 as 10000007 in his code, that generated incorrect tests. We sincerely apologize for such an error Edited by author 28.01.2025 02:06 Oleg Vasilenko (Chelyabinsk) Re: Wrong tests? // Задача 2181. Студент, или Туда и обратно 28 янв 2025 19:01 Thanks a lot for solving the issue! Also, what about the original contest results ? ( https://timus.online/monitor.aspx?id=1568 ) Anybody now with correct tests has AC for problem M ? (suppose that such tests were on this contest too). Edited by author 28.01.2025 19:43
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