CSP2021 J/S复赛游记(Csp2021 J / s semi finals travel notes)
Students in the same computer room:
October 3 to October 6
The school organized group s simulation competitions, but they were all original competitions, so they took \ (300 + \) every time
We began to train in the computer room at night and brushed some semi-finals in previous years. There was also a monthly competition on the 16th. After playing, the competition soared by 50 points.
In the last three days, I went through the zodiac green template and some blue templates.
This day was the last day of the training. During the training, the coach went straight to the black screen and talked about some strategies:
“You just change the desktop of the computer and write all the precautions for reading and writing files.”.
“Remember, don’t stick to a problem. You can go out to the bathroom and relax.”
These two sentences are the two sentences I remember most clearly and the two sentences I remember least clearly.
Group J (8:30 ~ 12:00)
7: 50 into the examination room, sat there for a long time before it began.
I sat far away from the big screen. After I wrote down the decompression password, my next door asked me to show him the password. It won’t be my cheating.
Read the question directly in 30min.
T1 was sent. After writing it, it also wrote violence against shooting. It took less than 10 minutes.
After opening T3, it is not difficult to find that it is a violent match. I also store each IP string in a similar way. The time complexity is \ (O (n ^ 2) \), and I also wrote a violent beat, which took about 1H.
After opening T2, it is found that the number of modifications is not much, so each modification is arranged in order, and an array is used to save the answers.
After that, it was found that for each modification, just let the number of modifications jump left or right, and optimize it to \ (O (n \ log n + Q + 5000n) \)
Beat with the code before optimization for 1H.
T4 feels that there is no rigorous method of complexity. After that, use the parallel query set to maintain the deletion number (use the parallel query set instead of the linked list), and then delete it violently. After deleting one, it jumps to the next block. If the next block is the same as the elements of this block, it jumps back all the time. It also writes the violent beat. It is set that there are \ (m \) blocks at the beginning, there are \ (K \) rounds to delete, and the complexity is \ (O (n + MK) \), I think it should be 70 points, sharing 30 minutes.
It was found that T4 seemed to be able to run \ (200000 \) under random data, and then tried hack without timeout.
Last less than half an hour has been shooting and checking documents.
On October 30, it was found that the leading zero was wrongly judged, and most of them would die if they couldn’t pass
Estimated score: \ (100 + 100 + 60 (100) + 70 (100) = 330 (400) \)
Luogu folk data: \ (100 + 100 + 100 + 100 = 400 \)
Preliminary evaluation on October 30: \ (100 + 100 + 70 + 80 = 350 \)
Group s (14:30 ~ 18:30)
The examination room asked us to enter at 14:00, but we were not allowed to enter the computer room until 14:20.
It took 30 minutes to read the questions.
It seems that T1 may be a strange data structure, T2 is an interval dp with a large number of codes, T3 should be a thinking problem, and T4 should not be done.
Then it opened tragically.
In the first hour, the title was regarded as “no more than \ (K \) super bracket sequences”, and then the first example output 4, which was directly hard adjusted to 1h after the start of the game.
After that, it took 10 minutes to think about T1, because although I wanted to listen to the coach, I still wanted to adjust T2, so I didn’t think of a reason. However, I wrote a 40 point violence in 10 minutes and then did T2.
After reviewing the T2 question, I found that there should be no more than \ (K \) of \ (s \), and then began to correct the solution.
After 20 minutes, it is typed, but the second sample output is 28. I started adjusting.
As a result, dev CPP in the examination room does not support debugging (I don’t know why, this is also the case in the morning), and can only output debugging.
After 1 hour of direct adjustment, it was found that there was no duplication judgment and started writing again. After writing, it was found that the output was 20. I don’t know whether the writing hung up or some repeated cases were not judged.
It was adjusted to half an hour before the end of the debugging… I went to write the 40 of T3. Maybe I was very angry and wrote a DFS for 20 minutes.
In the last 10 minutes, I could only stare at the T2 code in despair. I couldn’t do anything except checking the file.
In the last five minutes, I began to recall the T1 abandoned by me, and actually came up with a positive solution: calculate the number of corridor bridges where each aircraft stops with a segment tree or some data structure, and then open a bucket to calculate the answer.
After leaving the examination room, I found that T2 will also repeat
Estimated score: \ (40 + 0 + 40 + 0 = 80 \)
Luogu folk data: \ (40 + 0 + 40 + 0 = 80 \)
Initial comment on October 30: \ (60 + 0 + 40 + 0 = 100 \), T1 gave me 20 more points, but I still didn’t have 1 =.
UPD November 8: it was found that \ (1,2, \ cdots, n \) of the \ (2n \) number of T3 not seen in the examination room appeared twice respectively. After seeing it, you will do it
T3 of group J may be my failure this time, and I was stuck with \ (30 \) points. Although I took the right shot, I didn’t take this problem, which shows that I should not only take the right shot, but also give my own data.
Group s is the biggest tragedy. T2 is a big pit, but I have to jump in.
Finally, I will write the code handed in last year. Maybe I can get higher scores last year.
But in fact, if I deal with it, will it be too much, so my strength is not enough. And when you think of the solution, you can’t rush to write code. You should first see if there are other situations on the draft paper, and start writing code under the condition of ensuring the correctness of the solution and understanding the details of the code.
Of course, the strategy is also problematic. First get 40 points for t1ac and T3 and then write T2. In this way, the mentality may be better.
And T3 actually missed the conditions… This shows that we should look at the questions carefully and can’t miss the conditions.
Did I really remember the two words of the coach
The OI competition in junior high school is almost over, and there will be a high school entrance examination next. It’s best to study in the high school Department of our school.
This is just a test of the water, although almost all the things learned this year were not used in the competition.
I hope I can go back to the computer room after the high school entrance examination and see those familiar faces again.
- You can’t just shoot, you should also produce your own data
- When you think of the solution, you can’t rush to write code. You should first check whether there are other situations on the draft paper, and start writing code under the condition of ensuring the correctness of the solution and understanding the details of the code
- To maintain a good attitude as much as possible, you can go out to relax if you get stuck in a problem
- You can’t always stick to a problem and learn to choose
- We should look at the questions carefully and not miss the conditions of the questions