Info and problems are available at https://adventofcode.com/2025
Each day's solutions are in a subdirectory, 01, 02, etc.
Solutions are C++. Compile with:
g++ -std=c++20 -Wall -g -o doit doit.cc
There are occasional problems that need something special; in that case a comment at the start of the file will say what to do.
Example inputs, if any, are called input1, input2, etc.
The real input, as downloaded from the AOC website, would be called
input, though my inputs are not included in the repository.
Input is on stdin, output is printed to stdout. Run part 1 as ./doit 1 < input and part 2 as ./doit 2 < input
Sometimes I might go back and revisit a problem in a different
(usually more efficient) way. Alternatives will be other .cc files
starting with doit.
Here's my list of recommended problems for the year, along with direct links. Recommendations are based on a combination of factors: perhaps the problem admits an unusual and clever solution, or perhaps it would allow an interesting visualization, or perhaps the problem description itself was cute. In whatever way, I found the problem unusually fun. Each of these problems is either ⭐ (recommended) or ⭐⭐ (highly recommended).
- Day 2: Gift Shop ⭐ Brute force works, but it's interesting to do it faster
- Day 8: Playground ⭐ It's kind of obvious what to do, the question is how to do it quickly
- Day 9: Movie Theater ⭐⭐ This is cute and has various ways to approach it
- Day 10: Factory ⭐/⭐⭐ I'm of mixed minds about part 2; it likely requires certain knowledge to do fast, but perhaps if you're very clever you can manage without. (I'm not clever enough.)
Overall I give this year ⭐. It has some neat puzzles, but I kind of miss the full 25 days.
These are my AoC repositories for previous years (all C++, mostly the same format as this year). Years that I thought were more fun are rated with ⭐ or ⭐⭐.
