PAP Zig

Advent of Code style coding challenges in Zig.

Structure

Each task is organized in its own folder under src/:

src/
├── day01/
│   ├── solution.zig    # Solution code and tests
│   └── input.txt       # Input data (optional)
├── day02/
│   ├── solution.zig
│   └── input.txt
└── ...

Usage

Running tests

Run all tests for all tasks:

zig build test

Running the main executable

zig build run

This simply prints a message directing you to run tests.

Debugging Tips

VSCode LLDB Format Specifiers

When watching variables in the VSCode debugger, you can change the display format by adding a format specifier after the variable name:

variable,b       # binary (useful for bit patterns)
variable,x       # hexadecimal
variable,d       # decimal
variable,o       # octal
variable,c       # character

Example: To view a u8 byte as binary instead of hex, add byte,b to the Watch window.

This is particularly useful when debugging instruction encoding where you need to see individual bits.

Zig Print Debugging

Add debug output in your tests or solution code:

const std = @import("std");

// Print to stderr (won't interfere with test output)
std.debug.print("byte value: 0b{b:0>8}\n", .{byte});  // binary with leading zeros
std.debug.print("byte value: 0x{x:0>2}\n", .{byte});  // hex with leading zeros
std.debug.print("byte value: {d}\n", .{byte});         // decimal

Running Individual Tests

Run tests for a specific task:

zig build test --summary all

Filter tests by name:

zig test src/part1.zig --test-filter "specific test name"

Adding a new task

1. Create a new folder: src/dayXX/
2. Add a solution.zig file with this template:

const std = @import("std");

pub fn solve(input: []const u8) !u32 {
    // Your solution here
    _ = input;
    return 0;
}

test "dayXX example" {
    const input = "example input";
    const result = try solve(input);
    try std.testing.expectEqual(@as(u32, 0), result);
}

3. (Optional) Add an input.txt file and load it with @embedFile("input.txt")
4. Add your task name to the tasks array in build.zig:

const tasks = [_][]const u8{
    "day01",
    "day02",
    "dayXX", // Add your new task here
};

5. Run zig build test to verify your solution