YoungForest's blog

I was eight minutes late because of showering; otherwise I should have been able to enter the top 500.

This biweekly contest was a disguised hand-speed contest, with 141 people solving all four problems. The rest was a competition of speed on the first three problems.

I smoothly finished the first three problems in 10 minutes, but thought about Q4 for an hour without making a major breakthrough.

Although I had a few clues and felt it was a DP problem, afterward I found that the problem had already gone beyond the syllabus, so not solving it was normal.

Contest link

I did not participate in the previous LC-CN spring and fall contests, because our lab used to hold group meetings every Saturday afternoon, which perfectly conflicted with the contest time. Now my advisor has changed to holding small group meetings on weekdays and a large group meeting once a month, so I finally had the chance to participate in the 2021 Spring Contest.

1822. Sign of the Product of an Array

A warm-up problem. Count how many negative numbers there are and whether there is a 0.

Contest link

LCP 28. Purchase Plans

1816. Truncate Sentence

A warm-up problem. Let me emphasize again: string problems are suitable for Python. You really only need to describe the problem.

Recently, because I relaxed my problem-solving practice, my contest level has also declined somewhat. But this is something I did deliberately. Previously, I frantically solved 1k+ problems. Later, after hitting a bottleneck, I changed to solving three problems per day: one daily problem on the China site, one daily problem on the US site, and one daily problem from the Cruel Coding group. They had points and red-packet rewards respectively. Now I am basically at zero problems per day, only continuing to participate in weekly contests to maintain feel and get some joy.

Admittedly, problem solving and contests are very fun and addictive. I have long been unable to stop.

But because I am facing the pressure of graduation and the graduation thesis, I deliberately controlled the time and investment I put into problem solving.

I do not know whether you can understand this, but when writing a thesis, anything can become a temptation. Problem solving, which I usually like a lot, becomes an even bigger temptation and escape. At root, writing papers and doing experiments are truly too painful.

It does not even have to be problem solving. Anything that stops me is enough: reading books, watching movies, browsing forums.

There is no way around it. The thesis always forces me to put my main energy into it. I am not a person with strong enough willpower.

Therefore, I deliberately kept myself away from problem solving. Tasting only the joy of weekly contests is enough.

Because of my declining level and my China-site rating being too high, 2400+, I have basically moved to the US site now. The US-site account has a rating below 2200 and still has quite a bit of room to rise. Competing there is also not too stressful.

Previously on the China site, I dropped twice in a row and almost fell out of the 2400 club.

I plan to first push my US-site rating to 2400 as well. This way I do not put all my eggs in one basket, and my rating will be more stable.

Auto daily health report solution for BUAA.

It was check-in time again. I had been doing this brutal check-in for five consecutive weeks. And honestly, I did not feel the problems were that easy this time. I got 5 WAs and my mental state more or less exploded, but the ranking was still not ideal. It feels like LeetCode is getting more and more competitive.

Motivation

Following the problem in the previous post, Fixing Ubuntu Desktop VPN Access to Public Internet Resources, I tried configuring a jump host to access machines at the Hangzhou Research Institute.

In my research work, my MacBook could not connect to OpenVPN and therefore could not access the Hangzhou Research Institute machines. My Ubuntu desktop already had the VPN configured and could access the servers. I now wanted to route through the Ubuntu desktop so the Mac could “directly” access the Hangzhou Research Institute. Abstracting the problem:

• A can access B
• A cannot access C
• B can access C
• I now want A to access C

Since I mainly use SSH at work, the problem becomes: A logs in to C directly through SSH.
After persistent online searching and experiments, I summarized two techniques and methods that can achieve my goal.

• SSH proxy
• SSH tunnel

Over the weekend, I completely wasted three contests.

I did not participate in the biweekly contest, was half an hour late to the weekly contest, and then immediately participated in Kick Start. I was already done for.

In the future, before contests, I still need to conserve energy and compete properly.

For the fourth problem, I actually had an idea at the end, but unfortunately there was not enough time. I had previously done similar problems using Trie to handle XOR, so the impression was still quite deep.