Daily

This problem I actually liked, first of all it at least a bit smells like real world problem. Second, not very hard, exactly for 30-40 mins

https://leetcode.com/problems/vowel-spellchecker/description/?envType=daily-question&envId=2025-09-14

#daily

rephrasing question:
given list of words, and list of queries, return word per query using the following rules:

- if word is EXACTLY matched - return it
- if word is matched EXACTLY but case insensitive (w1.lower() == w2.lower()) -> return the first occurence from the word list. e.g. I have KiTy as query, and list [kITY, KiTY] - I should return kITY as it is the first.
- if word is matched both lowercase, but on the places of vowels there might be any other vowel (also return the first)

Daily

Easy, one minute problem - go and collect the coin

https://leetcode.com/problems/maximum-number-of-words-you-can-type/description/?envType=daily-question&envId=2025-09-15

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Daily

Easier than hard if you know the formulas and coecistance of least common multiple (LCM) and greates common divisor (GCD).

https://leetcode.com/problems/replace-non-coprime-numbers-in-array/description/?envType=daily-question&envId=2025-09-16

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Daily

Today is a bit late, was having students for system design.
I liked today's daily a lot. Small hint - think of something like lazy loading + MVCC in postgres, it will lead you to a correct answer.

https://leetcode.com/problems/design-a-food-rating-system/description/?envType=daily-question&envId=2025-09-17

I found system design question, that does not have solutions on the open internet. If you are looking for a challenge in system design - try designing "Virtual waiting room" aka "Virtual waiting queue".

https://www.cloudflare.com/en-gb/application-services/products/waiting-room/

This is the "clever" FIFO sticky rate limiter that is needed for example in case of ticketmaster for Taylor Swift traffic spike (14M req per sec).

How it works: it handles all 14M requests, and in FIFO manner it lets the first users to start booking, but still allowing only static amount of users to book (let's say 20k) simultaneously. While you are in queue your position and how many people before you are shown on the page. Once it is your turn - the page will load ticketmaster seat selection map.

How would you do it?

Daily

Pretty similar question to yesterday's. Learning how we can use "soft deletion" to make better complexity

https://leetcode.com/problems/design-task-manager/description/?envType=daily-question&envId=2025-09-18

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Random offline system design

Daily

Easy. Just 1 timesaver: better to use map instead of array

https://leetcode.com/problems/design-spreadsheet/description/?envType=daily-question&envId=2025-09-19

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Daily

The actual problem is quite interesting and tests different datastructures.

Also fucking constraints are misleading (I will explain in the solution)

https://leetcode.com/problems/implement-router/description/?envType=daily-question&envId=2025-09-20

However I believe that the amount of code produced here matches rather hard problem.

#daily

well, agree, this week was good, without math shit

We are living in crazy time. If algorithm does not know you - you are not allowed to watch youtube

Daily

A bit messy with code, but it is not much harder than yesterday's mid.

However, there is interesting topic for which Datastructures to use here (check solution in comment)

https://leetcode.com/problems/design-movie-rental-system/description/?envType=daily-question&envId=2025-09-21

#daily

(((((((((

first I switched from c# to javascript, cause it is less messy, and realized, JS does not have minheap.

So I switched to python, that has heapq, and even less messy so that now I don't have sorted set with tasty O(log n)