Advent of Code - C++

This repository contains a C++ template for Advent of Code, supporting multiple years.

Features

• Multi-year support - Organize solutions by year (2025, 2024, etc.)
• CMake-based build system - Easy compilation and dependency management
• Google Test integration - Unit tests for each day's solution
• Automatic input fetching - Download puzzle inputs directly from adventofcode.com
• Performance measurement - High-precision execution time tracking
• Modular structure - Each day is a separate module with its own tests
• Day generator script - Automatically scaffold new day solutions
• Google C++ style enforcement - clang-format integration

Project Structure

• Root Files:

  • CMakeLists.txt - Root build configuration
  • .clang-format - Google C++ style configuration
  • .clang-format-ignore - Exclude directories from formatting
  • main.cpp - Main runner with performance measurement
  • .env.example - Template for AOC session cookie

• scripts/ - Build and generation scripts

  • generate_day.sh - Day scaffolding generator
  • check_format.sh - Format verification script
  • templates/day/ - Template files for day generation
    • solution.h.template
    • solution.cpp.template
    • test.cpp.template
    • CMakeLists.txt.template
    • input.txt.template
    • input_test.txt.template

• src/ - Source code organized by year

  • common/ - Shared utilities
    • utils.h/cpp - String parsing, file I/O helpers
    • input_fetcher.h/cpp - AOC input downloader
  • YYYY/ (e.g., 2025, 2024) - Year-specific solutions
    • day_N/ - Individual day solutions
      • CMakeLists.txt - Build configuration
      • solution.h/cpp - part1() and part2() implementations
      • test.cpp - Google Test unit tests
      • tests/ - Input files
        • input_test.txt - Example input from puzzle
        • input.txt - Real puzzle input

• build/ - Generated build directory (not in version control)

Prerequisites

• C++17 compiler (GCC 7+, Clang 5+, MSVC 2017+)
• CMake 3.14+
• libcurl (for input fetching)
• clang-format (optional, for code formatting)

Installing Dependencies

macOS:

brew install cmake curl clang-format

Ubuntu/Debian:

sudo apt-get install cmake libcurl4-openssl-dev clang-format

Arch Linux:

sudo pacman -S cmake curl clang

Setup

1. Clone or navigate to this repository

2. Configure AOC session cookie (for automatic input fetching):

   cp .env.example .env

   Edit .env and add your session cookie:

   • Go to adventofcode.com and log in

   • Open browser DevTools (F12) → Application/Storage → Cookies

   • Copy the value of the session cookie

   • Paste it in .env:

     AOC_SESSION=your_session_cookie_here
     

3. Build the project:

   mkdir build
   cd build
   cmake ..
   make

4. Setup LSP/clangd support (for editor integration):

   The project is already configured to export compile commands. After building, create a symlink in the project root:

   ln -sf build/compile_commands.json compile_commands.json

   This enables clangd (used by VSCode, Neovim, etc.) to provide proper code completion and diagnostics.

Usage

Command-Line Options

./aoc [options]

Options:
  -y, --year YEAR    Specify year (default: 2025)
  -d, --day DAY      Specify day (1-25, default: all days)
  -p, --part PART    Specify part (1-2, default: both parts)
  -h, --help         Show help message

Examples

# Run all days of 2025 (default year)
./aoc

# Run all days of 2024
./aoc --year 2024

# Run day 1 of 2025
./aoc -d 1

# Run day 5 of 2024
./aoc -y 2024 -d 5

# Run day 10, part 2 only
./aoc -d 10 -p 2

# Run 2024 day 5 part 2
./aoc --year 2024 --day 5 --part 2

The runner will:

• Automatically fetch inputs if not present (requires session cookie in .env)
• Run the specified solutions
• Display results in a formatted table with execution times

Running Tests

# Run all tests
cd build
ctest --output-on-failure

# Run specific day tests
./2025_day_1_test
./2024_day_1_test

Adding a New Day

Automated Method (Recommended)

Use the day generator script:

./scripts/generate_day.sh <year> <day>

Example:

./scripts/generate_day.sh 2025 5

This will:

1. Create the directory structure: src/2025/day_5/
2. Generate all necessary files (solution.h, solution.cpp, test.cpp, CMakeLists.txt)
3. Create placeholder input files
4. Update main.cpp with includes and runner calls
5. Ready to rebuild and implement!

Next steps after generation:

Note: the generation script is already doing this now.

cd build
cmake ..
make
./aoc -y 2025 -d 5  # Fetch input and run

Code Style Enforcement

This project uses Google C++ Style Guide enforced via clang-format.

Format Code

# Auto-format all C++ files
cd build
make format

Check Formatting

# Verify formatting without modifying files (useful for CI)
cd build
make check-format

The .clang-format file in the project root defines the formatting rules. All code should be formatted before committing.

Utility Functions

The common/utils.h library provides helpful functions:

• readFile(filepath) - Read entire file as string
• readLines(filepath) - Read file as vector of lines
• split(str, delimiter) - Split string by character
• splitWhitespace(str) - Split by any whitespace
• trim(str) - Remove leading/trailing whitespace
• toInt(str), toLong(str), toLongLong(str) - String to number conversion

Example Output

Advent of Code - C++ Solutions
================================
Running all available solutions for year 2025

+=======+======+======+==================+===============+
| Year  | Day  | Part |      Answer      |   Time (ms)   |
+=======+======+======+==================+===============+
|  2025 |    1 |    1 |            54321 |         0.145 |
|  2025 |    1 |    2 |            98765 |         0.203 |
|  2025 |    2 |    1 |             1337 |         1.256 |
|  2025 |    2 |    2 |             9001 |         2.103 |
+=======+======+======+==================+===============+
| Total time:         3.707 ms                           |
+=======+======+======+==================+===============+