Congratulations to the contestants that made it to world finals!!
I think this was one of the most competed regionals I've ever seen!
I feel like the quality of the problems has been going up in the past 10 years, so congratulations to all of the problem setters as well!
Here I give a subjective difficulty to the problems:
- Easy: DLN
- Medium-Easy: CEK
- Medium-Hard: BFHJ
- Hard: AGI
- Very Hard: M
For Mexico solving all of Easy, Medium-Easy and 2 of the Medium-Hard would guarantee pass to world finals.
For other regions solving some/all of the Medium-Hard would also guarantee pass.
Every problem was solved during the contest by at least 1 team, congratulations to the teams that solved the harder problems!
DP was the most common topic it could be used in 6 of the problems, also for all DP problems (except L) they required a non-trivial transformation or optimization.
Notes on M: It was very hard, I think it was comparable in difficulty to https://open.kattis.com/problems/firstofhername. Would recommend finalists to solve this problem.
Link to editorial: https://github.com/Diego1149/ICPC-Latam-2020
For the difficulty in the editorial I assigned it based on the relative difficulty of the contest itself, meaning 1 to the easiest, 10 to the hardest.
Let me know if you have any questions or think I should update any of the editorials!
Hack for your M solution.
That's true, thanks for noticing, I'll have to learn suffix array to be able to solve it properly :P