Daily (314/373 streak until LC cap)

We have met this q as daily some time ago, very easy, 1 min coding.

https://leetcode.com/problems/find-the-highest-altitude/description/?envType=daily-question&envId=2026-06-19

#daily #easy #nopattern

Sorry for the silence, everyone - I know some of you were worrying. I'm currently going through a tough personal time right now. Overall, everything is going to be okay, but I just need a little time to recover.

Please keep doing your daily leetcode. I promise I will catch up with all of the problems and post here soon. In the meantime, I’m already planning the next article: Concurrency and Race Conditions for System Design (including real, practical applications).

Soon we are gonna return the regular pace: at least 1 post a day.

Hello all new people, probably from Anna's meet, if you are from somewhere else - pls do let me know, maybe I should say kudos to somebody else.

Quick intro about the channel, and what we are doing here is in "replied".

Btw, Anna is writing stuff here: https://nammemememe.substack.com

you might get a lot of interesting things about FAANG interviews, offers, how to prep, etc.

Now there is going to be bunch of skipped daily leetcode qs that I was solving all that time but never posted. You can skip up until it will be the last one which is today:

1846. Maximum Element After Decreasing and Rearranging

Daily (315/373 streak until LC cap)

Pretty tough one, but interesting.

https://leetcode.com/problems/maximum-building-height/?envType=daily-question&envId=2026-06-28

#daily #hard #nopattern

Daily (316/373 streak until LC cap)

The problem explicitly asks for counting sort -> so just perceive it as good counting sort reminder.

#daily #medium #pattern

Daily (317/373 streak until LC cap)

Pretty easy, but cool problem for challenging some of the leetcode problems. Recommended. Also it is special case of this problem https://leetcode.com/problems/rearrange-characters-to-make-target-string/submissions/2049315140/.
So you can solve 2 problems with one codebase.

https://leetcode.com/problems/maximum-number-of-balloons/description/?envType=daily-question&envId=2026-06-28

#daily #easy #pattern

Daily (318/373 streak until LC cap)

This is hedge fund level of problems. Do not recommend, bullshit and useless.

https://leetcode.com/problems/number-of-zigzag-arrays-i/description/?envType=daily-question&envId=2026-06-28

#daily #hard #nopattern

Daily (319/373 streak until LC cap)

Same as prev one, but tighter constraints. Again, don't recommend, it is the problem they ask in hedge fund, not in FAANGs.

https://leetcode.com/problems/number-of-zigzag-arrays-ii/description/?envType=daily-question&envId=2026-06-28

#daily #hard #nopattern

Daily (320/373 streak until LC cap)

Easy one for bruteforce, pretty hard for the optimized O(n) solution. But bruteforce will pass here.

https://leetcode.com/problems/count-subarrays-with-majority-element-i/description/?envType=daily-question&envId=2026-06-28

#daily #medium #pattern

Daily (321/373 streak until LC cap)

Same as previous problem, but tighter constraints. You will need to remember some variation of Boyer–Moore algo with additional things on top. Pretty complicated one

#daily #hard #pattern

Daily (322/373 streak until LC cap)

Not bad problem, not that hard, however no pattern.

https://leetcode.com/problems/find-the-maximum-number-of-elements-in-subset/description/?envType=daily-question&envId=2026-06-28

#daily #medium #nopattern

Daily (323/373 streak until LC cap)

Now today's problem (all previous ones where for my long time away)

This one is pretty easy, I would rate it as easy. Go for it.


https://leetcode.com/problems/maximum-element-after-decreasing-and-rearranging/description/?envType=daily-question&envId=2026-06-28

#daily #medium #nopattern

we have synchronized.

Daily (324/373 streak until LC cap)

Easy if using O(n^2) or built-in function. But pretty tough if using some special algo like KMP.

https://leetcode.com/problems/number-of-strings-that-appear-as-substrings-in-word/description/?envType=daily-question&envId=2026-06-29

#daily #easy #nopattern

Warm up for Concurrency / Multithreading in System design. Let's say we have plane seat booking system like Kiwi or event booking system like Ticket master.

The domain is simple, multiple users might click on the same seat and double book it. Solution: lock the seat for 10 minutes and allow single user to proceed with payment or timeout before others can lock it as well.

The reason for double booking problem here.

We are assume our backend is multithreaded, however even in single threaded nodejs, the same thing can happen because of different network delays.

- 2 threads read the seat, and see status = "available", which means we can write "reserved".
- both threads are writing 'reserved' and putting their customer that is doing the request.
- you see that red customer2 (red) overrides whatever was written by customer1 (blue). However customer1 (blue) got successful write, no errors, nothing.