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+# Advent of Code
+
+The [Advent of Code](https://adventofcode.com) is an online programming
+contest that takes place every year in December. It works like an
+[advent calendar](https://en.wikipedia.org/wiki/Advent_calendar), except
+each day instead of a piece of chocolate or a sweet you get a new problem
+to solve.
+
+I have taken part in this contest for the first time this year, after
+an email from a colleague that mentioned prizes for the winner of our
+private leaderboard. Even without any prize, if it is a challenge
+then I must accept it!
+
+*Warning: if you are still trying to complete the problems, you may find
+minor spoilers ahead, but nothing game-breaking.*
+
+## Choosing my weapons
+
+As I was initially not planning on taking part in the challenge, I did
+not have much time to decide which language or tools to use. I opted for
+solving the problems in C, because it is the language I worked with the
+most recently, but in hindsight it would have been more convenient to
+refresh my Python or C++ skills.
+
+In the end using a more limited language did not make a big difference: the
+easy problems were still easy, some of the hard ones became a bit slower
+to type out. I also had some fun implementing some basic data structures,
+for example [heaps](https://en.wikipedia.org/wiki/Heap_(data_structure))
+for [day 17](https://adventofcode.com/2023/day/17).
+
+## The fun
+
+Overall, I really enjoyed solving these problems! I liked the diverse
+set of techniques that were needed: graph algorithms, dynamic programming,
+computational geometry... a very nice selection of brain teasers!
+
+I also liked the fact that the difficulty increased *on average*, but
+sometimes a hard problem was be followed by an easier one. This way,
+even if I found a problem particularly hard, I could still hope that
+the next one would be quicker to solve.
+
+I also liked that other people, including friends, colleagues and my
+girlfriend, were taking on the challenge at the same time. I enjoyed
+explaining my solution or asking my friends to explain theirs. By the
+way, my friend Jared has some in-depth explanation of his solutions
+in his [blog](https://guissmo.com/blog/) - check it out!
+
+## The ugly
+
+There were a couple of problems that I disliked, and all of them for
+the same reason: the problem was not solvable without taking advantage
+of specific properties of the input data that were not made explicit in
+the problem's statement.
+
+As a Mathematician, I am never going to randomly assume that a generic
+graph has a specific structure, or that just throwing the
+[lcm](https://en.wikipedia.org/wiki/Least_common_multiple) into my
+algorithm would make it work. So I was scratching my head for hours trying
+to solve a general problem that was very likely unsolvable, when I only
+had to solve a special case.
+
+However, as a Reddit user pointed out, the input data *is* part of the
+problem statement. Analyzing it to figure out what algorithm may work
+is a skill. I guess I learnt something from this.
+
+## Solutions
+
+If you are interested, you can find all my solutions on
+[my git page](https://git.tronto.net/aoc/) and on
+[Github](https://github.com/sebastianotronto/aoc). They are written in
+[C99](https://en.wikipedia.org/wiki/C99) without any external dependency
+other than the C standard library.
+
+Apart from the harder problems, I have not commented my solutions much,
+but you can send me an email if you want some explanation!