### chokudai's blog

By chokudai, history, 2 months ago, We will hold Toyota Programming Contest 2023 Spring Qual A（AtCoder Beginner Contest 288）.

The point values will be 100-200-300-400-500-500-600-600. Since this contest is used as a qualification round for a local event, the style of problems is modified a bit.

• Up to task C is usual.
• (the style of tasks D-Ex in this contest) is between (the style of tasks D-Ex in usual ABC) and (the style of earlier tasks in usual ARC).
• Tasks in the middle of this contest are slightly harder than usual. Later tasks are not too difficult.

We are looking forward to your participation! Comments (23)
 » 2 months ago, # | ← Rev. 2 →   How to do problem D? IMO problem D is of higher difficulty than usual one.
•  » » 2 months ago, # ^ | ← Rev. 2 →   yep it was harder..I solved it with some maths intuition. After a lot of case work I found thatFor a sequence of ${[L, R]}$ should be good if and only if.${A_i + A_{i - k} + A_{i - 2 * k} + .... A_p - A_{i - 1 - k} - A_{i - 1 - 2 * k} - .... A_{p-1} = 0}$where ${p < L}$ and ${L \le p + k}$.for all $i$, ${R - k + 2 \le i \le R}$My Submission
•  » » According to Kenkoooo Atcoder Problems, ABC288D may be the second Problem D (in 8 problems rounds) that difficulty is above 1600. It is even harder than the first one ABC227D. But I think that ABC288 is easier than ABC227 on the whole.
 » It looks like E is dp but i don't know how to solve it. Where can i find problems like this ?
 » 2 months ago, # | ← Rev. 2 →   screencastFor problem Ex, the solution in the editorial is a bit complicated. You can simply consider using the burnside lemma for all permutations on all $n$ numbers.
•  » » Could you please explain the burnside lemma solution?
 » Japan has a different definition for "beginner"
 » First I didn't see r-l+1>=k. I thought it was yet another irritating array corner problem. Then I thought it is kind of modulo sum, then all remainders in range should should be multiple of K except zero After so much time, thought to see in lens of math, Then I thought it might be of diff array technique. No luck I couldn't get any ideas. 
 » I know E is Dp but can't figure out states. Someone please Explain?
•  » » 2 months ago, # ^ | ← Rev. 2 →   The key observation in $E$ is that if we bought $2$ items $i$ and $j$ (\$i
•  » » » Thank you so much for your detailed explanation of problem E. I have got the definition of states and transition formula, but missed that mins[i][i-j] part, while I used C[i-j] instead. Your words "we can buy it first before buying any of the j items, or we can buy it after buying 1 of the j items and so on" really helps me a lot. Thank you!
 » Missed D by 5 mins, rip ratings...Tip: Never start a contest late, and that too by 5 mins. Spoiler 