AdventOfCode2024

Solver for Advent of Code 2024 puzzles. https://adventofcode.com/2024/

This is a single command line application for the puzzles written in C++23 with CMake.

Puzzle Input

This project does not contain the puzzle or example inputs as per the copyright notice of Advent of Code. In order to run the compiled application, the puzzle inputs have to be downloaded from the Advent of Code 2024 puzzle pages, and placed as text files into the AdventOfCode2024\data directory, e.g. AdventOfCode2024\data\historian_hysteria.txt, or AdventOfCode2024\data\example\historian_hysteria.txt for the unit tests. The application will output an error message with details if it cannot find an input file.

Tests

The solution contains a unit test project to help troubleshoot issues and prevent regressions in the solver class framework. These tests cover the solutions for provided examples and full data inputs. I did not find a definitive source for it, but the full data inputs seem to be user-specific, so adding my solutions as tests does not spoil the solutions.

Solutions

Day 1: Historian Hysteria

🔎 Puzzle: https://adventofcode.com/2024/day/1, ✅ Solver: HistorianHysteria.cpp

I'm using a std::multiset to collect and sort the values for both lists. This allows to use a single iteration of the left list and two iterations of the right list simultaneously to solve both parts. Nice application of iterators.

Day 2: Red-Nosed Reports

🔎 Puzzle: https://adventofcode.com/2024/day/2, ✅ Solver: RedNosedReports.cpp

Here, we have a few conditionals to determine on the fly which of the numbers would make the report safe if dropped. The amount of cases is actually quite manageable.

Day 3: Mull It Over

🔎 Puzzle: https://adventofcode.com/2024/day/3, ✅ Solver: MullItOver.cpp

A simple finite state machine crawling along the input character by character solves both parts nicely. The algorithm tracks whether mul instructions are enabled or not, but ignores this setting for part 1.

Day 4: Ceres Search

🔎 Puzzle: https://adventofcode.com/2024/day/4, ✅ Solver: CeresSearch.cpp

For this puzzle I added a class for points in two-dimensional space, so I can use these for simplifying directional computations. With that, the algorithm looks for all X and A for part 1 and 2, respectively, and tries to find the remaining characters, starting from that X or A.

Day 5: Print Queue

🔎 Puzzle: https://adventofcode.com/2024/day/5, ✅ Solver: PrintQueue.cpp

My implementation uses an ordering matrix (a two-dimensional boolean array) to track which page combinations are ordered, and then queries that matrix for each ordered combination of pages in a single line. The same matrix can then also be used for a custom sort function for part 2.

Thanks

• Alexander Brouwer for getting the project set up with CMake.

License

Copyright (C) 2024 Stefan Müller

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.