YoungForest's blog

How my investing journey began, what changed my thinking, and the lessons that still shape it.

I participated in Kick Start after a long absence. For the previous two years, because I wanted to go to Google, I had kept participating. But man proposes, God disposes: because of the pandemic, both internships and autumn recruitment basically fell through. I had participated in 10+ contests over more than two years, and they were “wasted” in that sense.
This year I joined purely out of interest. The result was indeed a 1000+ rank. Before, I was usually in the several hundreds.
I have to say that since last year Kick Start has become much easier and friendlier. Previously I often could only solve one and a half problems. Later, to broaden participation, three problems became four, and the overall difficulty also came down.

I missed the contest, then upsolved it after the contest.

1796. Second Largest Digit in a String

Warm-up problem. Count all digits, then scan from large to small to find the second largest one.

Because of research needs, I needed to connect to the Hangzhou Research Institute VPN before I could use GPUs for neural network training tasks.
However, after configuring OpenVPN on Ubuntu 18.04, I found a difficult problem: after connecting to the VPN, I could not access the public Internet, such as Baidu and similar websites. These were not sites outside the Great Firewall, but the “external network” relative to the local intranet. After disconnecting the VPN, I could access the public Internet, but could not access Hangzhou Research Institute resources. Since in daily work both the public Internet and the Hangzhou Research Institute intranet are basically indispensable, I spent two days investigating and fixing this problem. Also, other classmates using the VPN did not have similar issues, so I believed this was a problem specific to Ubuntu. The fix itself was simple, but the process of locating the problem was very bumpy.

Symptoms

After connecting to the VPN, I could ping Baidu’s IP address, but the browser could not open Baidu, and I also could not directly ping baidu.com. The browser could only open Hangzhou Research Institute and BUAA internal websites.
My initial judgment was that it was a DNS server issue, but after investigation I found the DNS configuration had no problem.
My guess was that when accessing external resources, the expected DNS resolution had no way to complete.

Yesterday I went out to repair my Mac because the screen kept flickering. Sure enough, for Apple products, AppleCare is necessary. Last time I repaired the keyboard; this time I repaired the screen, so all four sides have been replaced with new parts. I was out running around for a whole day and was especially tired. I woke up late this morning, and the contest started as soon as I got up. I had not had a sip of water or a bite of food.
After solving 3 problems for two consecutive weeks, I finally solved 4. At first I was quite pleased and thought I should not need to check in this week. Later I found the clown was actually me. Other contestants even thought this round was a speed round. I overcomplicated T3 and T4, so I was a bit slow and did not enter the top 500. My Cruel ranking also fell from 10+ to 40+. My rating will drop next week. I did not expect 3 problems to raise rating and 4 problems to drop it.

A crazy rating-gain round. I solved 3 problems in 13 minutes. The idea for the last problem was also relatively smooth. I hit two blockers: first, at the beginning I forgot to consider point pairs with no edge between them; second, I solved the complementary problem, but when returning the answer, I carelessly thought the total count was n^2, while in fact it is C(n, 2) = n * (n - 1) / 2. Debugging wasted quite a bit of time. If it had gone more smoothly, maybe the result could have broken through the sky and won the generous top-20 prize.

A 3-problem contestant, again. sad.

Since autumn recruitment ended, my enthusiasm for practicing problems and contests has declined day by day.
Previously I did three problems every day, China server, US server, and Cruel. Now I do zero problems a day. Of course, occasionally, when my weekly contest result is not enough to exempt me from check-in, I still need to do one problem per day.
In contrast, contest feedback is still quite strong. In the long term, rating and ranking growth provide motivation. In the short term, Cruel ranking and each contest ranking provide motivation, plus extra points as rewards. Also, after the weekly contest, I can get a red packet in the Cruel group and add a chicken drumstick for myself.

1773. Count Items Matching a Rule

Cause

Recently the pressure of graduation has been quite heavy, so I wanted to download a movie from Beiyouren and relax a bit. But I found that qBittorrent, the BitTorrent client I had always used for seeding and downloading, could no longer open. I searched online for quite a while for the cause and solution.

I finally confirmed that the culprit was a Mac update. qBittorrent was treated as an app with incomplete verification: Issue 11570.
There are two solutions:

Motivation

Recently, after watching some videos by “Banfo Xianren”, I became more interested in money. Besides taking out part of my savings to invest in A-shares, I also started thinking about how to increase passive income. I have always had the habit of writing a blog. I have been writing for more than five years and have accumulated over a hundred articles. Although daily page views are only in the dozens, even a small fly still has meat. Referring to some experiences from experts, I tried making money by placing ads.
Website ad revenue is generally connected through an ad network. In short, you only rent ad slots to the ad network. They place user-targeted ads there and pay you based on traffic.
For international audiences, the main option is Google AdSense. There are also some domestic options, such as Baidu.
Because my main job is as a programmer, and blog content is not limited by national borders, I chose Google AdSense as the ad provider. Google AdSense is very simple to configure.

Specific Steps