This year's Blue Bridge Cup final is over, and I'm not in a good mood after only winning a national third. . . Let’s briefly talk about the whole process and some impressions of the preparation for this national competition.
The provincial competition ended at the end of March. At that time, I talked about my feelings, that is, the question of water people is water, but I can brush down a large part of water people, and the most important thing is to get started. As for the national competition, I have never experienced it before. I only heard from the seniors. They were all miserable. They failed all six questions (at most one question) to get a national third, and having a national award is considered to be a weak school like us. Participating students have a basic return, of course, they did not dare to have any extravagant expectations, after all, the level is really not high. By the way, the Blue Bridge Cup has always had the nickname of "Violence Cup". Violent deception or something, I think this is actually just a joke. After all, the brute force cracking written by experienced people is better than ours. Weak violent gestures are definitely different (although I hate to admit it...)
Talk about the preparation process. Between the provincial and national competitions, I have only played two matches, not many. Before the national competition, there was a provincial competition (this provincial competition was organized by the province, the one played by the team), the school held the school competition, and my little friend and I AK all the problems, but we were sentenced to foul and our qualifications were disqualified. It's a pity that we lost the chance of this competition. . . (I was selected for this competition in my freshman year because I wanted to participate in the math competition, but I did not participate in the school competition. The state of the sophomore school competition was too bad, and I was brushed. This time I performed very well in the junior year, so I won’t let us go. Wait for the senior year, eh)
In order to add some drama to ourselves, we formed a team to participate in the school competition with the provincial normal university. The programming club of the normal university held this trial. Brother colleges are welcome to come and exchange, and many acquaintances from our school also formed a team to participate. A total of less than 300 groups participated, which was quite lively. The team in my group performed very well. They got 7 out of 11 questions and took the third place. The teacher in charge of the Normal University gave us prizes and souvenirs enthusiastically. Compared to the cold reception he received in his own school, although it was true that he fouled himself first in the school competition, he still felt very uncomfortable. . .
In addition to the two small-scale competitions mentioned above, I did not participate in other competitions, but I watched some of the questions on the OJ competition, and I usually follow up on the questions. According to the characteristics of the exam questions of the Blue Bridge Cup finals in previous years, our friends who are about to participate believe that the B group of the Blue Bridge Cup will not examine the commonly used things in ACM such as number theory, line segment trees, etc., at most it is to pack the title of the title. Turning a few more turns in the thinking, in fact, the more basic algorithms such as DP, search, dichotomy, and greed are examined. According to the situation we have analyzed, I think we should consciously strengthen this part of the basic training, that is, increase the difficulty in thinking. So I took LeetCode as a basic training, and added some questions with a certain thinking content to Luogu. I thought this was enough, but fate played a big joke on us. Unsurprisingly, the Blue Bridge Cup has become more difficult this year. Unexpectedly, the difficulty of this time is too great for our usual preparations.
Briefly describe the topic. When I opened the pdf of the test questions, I was shocked. Since it was the tenth anniversary of the Blue Bridge Cup, there were ten questions in the final. . . This disrupted my deployment a bit. After all, there were no more than six questions in previous years. This year, the questions will go up as soon as possible. Just a quick glance, WA, I feel like it's over.
The first question, the problem of ascending sequence, I wrote the example without reading it carefully, and I missed a situation and did not scan it.
The second question is similar to the Quartet Theorem. I also didn't pay attention to the condition that the same scheme cannot have the same number. It must be wrong to write a backpack and run casually.
The third question, I didn't understand the question, just skip it.
The fourth question, a typical TSP problem, my idea is the state pressure, but this topic is really disgusting, with the attributes of a big simulation, I don't want to write it.
The fifth question, the problem of the smallest sum of divisors. At first glance, it is number theory. Ah, if you are not prepared, violence will not come out. I spent a lot of time on this topic, mainly because I feel that although I have come into contact with number theory, I should be able to find some laws or something, which should be related to quality. It's related to factorization, but unfortunately I couldn't find it in the end.
The sixth question, string matching, dp or double pointer is fine, I should have written this question correctly, after all, I usually spit out this kind of question on LeetCode. . .
The seventh question is to find the number of squares. This question took me a long time. I didn’t know how to start at first. After thinking about it for a long time, I felt that it would be enough to find the regularity and repeat it. It took a while to repeat and verify. I don't know if the conclusion is completely correct, but it should be able to pass some test cases.
The eighth question is a typical search, but this question is also very annoying. At that time, I was confused and didn’t know how to optimize it, so I went straight to a deep search.
The ninth question, it feels like a minimum path coverage problem, but unfortunately I am not prepared. . .
The finale question, I was stunned when I saw it. I inquired many times and modified it at a single point. Isn't this Nima a line segment tree or a tree array? My god, why did I take the QAQ test without preparation. Looking back, the query block also requires the largest amount, so just disarm it. I don't have any boards on my back, not to mention that I don't know how to deal with this kind of block and seek the maximum, dp? I'm afraid it won't run out even in 100s. . . On the subway after the game, I happened to meet the classmate who was sitting across from me during the game. He was in the C++A group. He told us that the chairman tree should be used for this question. . .
Looking back, I can attribute the reasons for this poor performance to the following:
1. The preparation is really insufficient, and the strength is not enough. When I encounter some problems, I don’t know how to start because I don’t learn enough and the training is not in place. The strategy is not right. At that time, it was better to write the fourth question, because it is too troublesome to not write it. It is not the idea of the competition. . .
In short, in this final, I also recognized my own strength, or the strength of our small partners who participated in the competition together (one of them won the national second, he played better, and the others were national three). It’s still too bad. Usually, the training is not scientific and comprehensive, and I have not experienced systematic training. In addition, I don’t perform well on the spot, and it is normal to have no good grades. It is still necessary to maintain a normal heart.
Finally, let’s talk about number theory. I have learned a little bit of number theory sporadically, which is quite unsystematic. I have participated in mathematics competitions, but they are mainly based on functional equation inequalities, and number theory is basically not involved.
Reprinted in: https://www.cnblogs.com/messi2017/p/10931732.html