Advent of code

This is a community driven Java template and utility API for the annual Advent of Code event.

Setup

1. Clone this repository from GitHub as an IntelliJ repository (untested on other IDE's)
2. Add the AOC_SESSION_COOKIE environment variable to your gradle run config and set it equal to that of your session cookie after logging in to your AoC account.
   • Alternatively you can set a system environment variable and restart the IDE/terminal.
3. Execute the gradle application -> run task.

Creating and Running Solutions

Solution Packages

Create a package-info.java in the package which contains your solutions for a given year. Make sure to annotate it with the @AdventYear annotation, so we can pull the correct inputs.

Example:

@AdventYear(year=2024)
package org.togetherjava.aoc.solutions;

import org.togetherjava.aoc.core.annotations.AdventYear;

The package my contain any files or subpackages you wish, but as described next, the solutions need a specific structure.

---

Solution Classes

Solution implementations must be under an @AdventYear package to be runnable. Additionally, they must implement the PuzzleSolution interface, which provides methods that give an input type directly.

A useful shortcut for this is CTRL + I in IntelliJ, which implements missing methods.

Setting The Day

While @AdventYear explicitly defines the year, a solution can implicitly or explicitly define which day of the year.

Explicit Day Value

To explicitly set which day your solution corresponds to, use the @AdventDay annotation to override and ignore auto-detection.

Example:

@AdventDay(day = 1)
public class DayOne implements PuzzleSolution

Implicit Day Auto-Detection

If no @AdventDay annotation is provided, a default auto-detection is used instead. This will look for the first number in the class name in the range [1, 31], ignoring leading zeros. Therefore, the following examples would be parsed as:

Class Name	Implicit Day
Day1	1
Day02	2
Day003	3
AocDay4	4
AocDay05	5
Aoc2024Day6	6
Aoc2024Day07	7
Day8Attempt2	8

---

If neither implicit nor explicit days can be resolved, an error is thrown at runtime.

Puzzle Solution

The methods defined by PuzzleSolution return Object, which is because not all AOC answers are int or long. You may still return an int or long type, and it will be autoboxed into an object.

Here is an example implementation

public class Day01 implements PuzzleSolution {

	@Override
	public Object part1(PuzzleInput input) {
		return 123;
	}

	@Override
	public Object part2(PuzzleInput input) {
		return 456L;
	}
}

Running Solutions

The AocRunner class provides static access to run your solution implementations.

There are 3 method names: run, runPart1, and runPart2, which each have the following overrides:

Parameters	Description
()	Run today
(int year, int day)	Run the given day
(PuzzleDate date)	Run the given date
(Class<? extends PuzzleSolution> impl)	Run the given implementation

Below are examples of different runner invocations:

AocRunner.run(); // Detect and run the current day's solution
AocRunner.run(2024, 1); // Detect and run the AOC 2024 Day 1 solution
AocRunner.run(Day01.class); // Run the solution implemented in Day01
AocRunner.run(Day01BruteForce.class); // Run the solution implemented in Day01BruteForce

Multiple Solutions

If more than one class implements a solution for a given date, all of those implementations are registered internally. When trying to run them without a specific class reference (e.g. run(Day1BruteForce.class)) then the specific implementation chosen is not well-defined, and is whichever is reflectively found first.

Input Caching

Input files are fetched from the AOC web API to get your input data. To support AOC, we automatically cache the input responses on your local computer, preventing redundant API calls every time you run an implementation.

Local File Cache

Cached input files are stored locally in a path relative to your OS platform. This is done with the user.home system property. Relative to that, /.together-java/aoc/inputs/YYYY-DD-puzzle-input.txt is where the file is stored.

• Windows: %userprofile%/.together-java/aoc/inputs/

Session Cookie (AOC_SESSION_COOKIE)

Getting your session cookie

In Chrome, or other Chromium browsers such as Opera, OperaGX etc

1. Hit ctrl + shift + J to open up developer tools
2. Navigate to the application tab
3. Click cookies
4. Copy the session cookie

Modifiying Gradle run configuration / env

1. Go to your Gradle tool window

   • Tasks
     • application
       • Right-click run → Modify Run Configuration...

   

2. Click this box to add an environment variable
   

3. Name the environment variable AOC_SESSION_COOKIE and then paste the value of your session cookie from your browser in to the value box.
   

4. Hit okay and then execute the Gradle run task