On 13th June there was Codeforces round #649. In problem D during the round, there were only 137 test cases as the main test, so lot of people got AC during the round but afterward, the number of test cases was increased to 142 and many passed solutions were failing in those test cases. and this is not the first time this happened, In Codeforces Round #637 (Div. 2), problem D had only 24 test cases initially which allowed even greedy solutions to GET AC, which was failing in afterward added test cases. So is there any reason for this happening and will it be solved?

Solution That got AC during round But Failed when new test Cases were added:-

1. Codeforces round #649 D

2.Codeforces Round #637 (Div. 2) D

(P.S.:- These solutions got AC even after the system test as at that time there were fewer test cases but Now if you submit them, they won't pass as test cases got increased)

Hey everyone, CapJohn and I are creating a group to hold regular Mashup Contest as solving questions on practice are getting rather boring and we plan to simulate the environment of a real contest by competing with you guys.

In each contest, we will have questions from different rating levels [1500-2400] and the problems will be from past CodeForces contest. We think this will help us improve more effectively.

The Mashup Contest will only be held on days when there is no official contest. People with rating range 1400-2100 would be the best match for the group!

For all those who are interested, request(Group Link) or DM me or CapJohn and you will be added to the group and we'll start having the contests and utilize the quarantine time more efficiently. Mention your friends who might be interested!

Thank you!

Group Link

I was trying a problem on LCS topic and was stuck. It will be really helpful if anyone can provide me a hint to the problem.

Problem :-ADASEED