Advent? Of Code?

For those of you who don’t know what an Advent Calendar is - its basically a spepcial way to countdown the days to Christmas. Its generally a calendar or a box with flaps that one opens up for each day moving up to Christmas. Spreading a little bit of joy each day.

So Eric Wastl created Advent of Code - an advent calendar of coding questions! As mentioned in his words - “Advent of Code is an Advent calendar of small programming puzzles for a variety of skill levels that can be solved in any programming language you like.”.

I found out about it in Uni, however never had the time to properly work on it. While the puzzles range from easy to hard, what’s really amazing about AoC is the AMAZING community that can be found in the AoC subreddit. Many solve the puzzles to learn programming / a new language / get more comfortable. However a lot of people extend it a lot - competing to finish it the fastest, visualizing the solutions, optimizing them to run under a millisecond or even solving it on the most unique ways - like on a graphics calculator!

This was the first (and def not the last) year I finished all 25 days. A bit rusty, my best performance was at 793 globally for day 4. Pretty good, but a lot to improve :D

Top Mentions for problems in 2025

Here are a list of my most memorable problems for the year!

4. Day 7 - Solving a problem on the phone using Repl

I was travelling one weekend, and since I was just on the train doing nothing, I wanted to still complete it using my phone. It was still in the early days, but hey was quite cool typing it out on my phone instead of my laptop :D

3. Day 21 - The multi multi multi layered recursive problem

Day 21 was in hindsight a standard recursive / DP problem. However it had a couple of tweaks that stumped me for the whole day. Firstly it had a couple of possible paths which increased the complexity a lot. However one of the paths was always better than the other, so I didn’t really have to worry about exploring that many options. Secondly I just needed a count (length of the string), though the idiotic me tried to generate the whole string and ran into memory issues.

Hair pull moment after realizing my mistakes. Still a fun problem to solve!

2. Day 17 - The Chronospatial Computer

Day 17 was one of the most fun solutions. In this program, you couldnt write code to find the solution for any input in general. Here you had to backwork from the given input and work around it. This required some analysis of the requirements and some trial and error to find the pattern and solve it. Very fun indeed! 5 / 5 ☆

1. Day 14 - The Christmas Tree!!!

I think a favourite of a lot of people this was the question in part 2 of the puzzle for day “If they’re the same type of robots, they should have a hard-coded Easter egg: very rarely, most of the robots should arrange themselves into a picture of a Christmas tree. What is the fewest number of seconds that must elapse for the robots to display the Easter egg?”

Huh? Picture of a Christmas tree? We only had a grid of points without any idea of what the tree would look like. I ended up looking at the subreddit in case I missed something in the question and ended up coming across how the answer would look like. However I loved the community and the different approaches people took - this one where someone calculated the entropy of the grid at different time points was so creative!

All in All, AoC is a really fun problem with an amazing community! Go check it out in the meantime, and ofc see you in December 2025!