Helpers for Advent of Code

This crate contains some helper methods that I regularly use in my Advent of Code solutions.

Processing of command line arguments

args::get_args

Reads the command line arguments and checks whether the correct number of arguments are present.

Example

use rdcl_aoc_helpers::args::get_args;

fn example1() {
    let args = get_args(&["<input file>", "<init>"], 1);
    println!("{:?}", args);
}

fn example2() {
    let args = get_args_repeating(&["<input file>", "<x1> ... <xn>"], 1);
    println!("{:?}", args);
}

Direction

The Direction enum is a convenient enum if you are dealing with cardinal directions (i.e. up, down, left and right). It allows you to turn and travel (using the CanTravel trait).

Error handling

error::WithOrExit

This trait adds a or_exit_with method. The purpose of this method, is to allow you to easily let your program terminate with a specific exit code. It has been implemented for Result and Option. The implementation for Result requires that the associated error type implements fmt::Debug.

Example

use rdcl_aoc_helpers::error::WithOrExit;

fn main() {
    some_operation_that_returns_a_result()
        .or_exit_with(25);
}

error::ParseError

A generic error containing just a message. It implements fmt::Display and fmt::Debug, and it can be converted from io::Error and num::ParseIntError.

Example

use rdcl_aoc_helpers::parse_error;
use rdcl_aoc_helpers::error::ParseError;

fn example_with_params(param: u8) -> Result<(), ParseError> {
    if process(param) {
        Ok(())
    } else {
        Err(parse_error!("Failed to process param: {}", param))
    }
}

fn example_without_params() -> Result<(), ParseError> {
    if process() {
        Ok(())
    } else {
        Err(parse_error!("Failed to process"))
    }
}

I/O operations

input::MultilineFromStr

This trait is inspired by the str::FromStr trait, and allows you to parse input where data might span several lines.

Example

use rdcl_aoc_helpers::error::ParseError;
use rdcl_aoc_helpers::input::MultilineFromStr;

pub struct Record {
    items: Vec<u8>,
}

impl MultilineFromStr for Record {
    type Err = ParseError;

    fn new() -> Self {
        Record {
            items: Vec::new(),
        }
    }

    fn indicates_new_record(&self, line: &str) -> bool {
        line.is_empty()
    }

    fn parse(&mut self, line: &str) -> Result<(), Self::Err> {
        if !line.is_empty() {
            self.items.push(line.parse::<u8>()?);
        }

        Ok(())
    }
}

input::WithReadLines

This trait adds a read_lines method. The purpose of this method is to read the lines from some source (e.g. a file), and then convert each line to a specific type. As an argument, this method takes an exit code that should be used if processing the source fails, and it returns an iterator. This trait has been implemented for fs::File.

Example

use rdcl_aoc_helpers::input::WithReadLines;

fn main() {
    for item in File::open("./my-file.txt").read_lines::<u8>(1) {
        println!("Item: {}", item);
    }
}

input::WithReadMultiLines

This trait adds a read_multi_lines method. It's the equivalent of input::WithReadLines, but rather than depending on str::FromStr, it depends on input::MultilineFromStr.

Example

use rdcl_aoc_helpers::input::WithReadMultiLines;

fn main() {
    for record in File::open("./my-file.txt").read_multi_lines::<Record>(1) {
        println!("Item: {:?}", record);
    }
}

#[derive(Debug)]
struct Record { /* ... */ }
impl MultilineFromStr for Record { /* ... */ }

input::WithAsRecords & input::WithAsMultilineRecords

These traits allow you to easily convert an object to a vec of items of the required type.

Example

#[cfg(test)]
mod tests {
    use rdcl_aoc_helpers::input::WithAsRecords;
    use rdcl_aoc_helpers::input::WithAsMultilineRecords;

    use super::*;

    #[test]
    fn test_simple() {
        let input = vec!["1", "2", "3", "4", "5"]
            .as_records::<u8>()
            .unwrap();

        assert_eq!(input, vec![1, 2, 3, 4, 5]);
    }

    #[test]
    fn test_multiline() {
        let input = vec!["1", "2", "", "3", "4", "", "5"]
            .as_multiline_records::<Record>()
            .unwrap();

        assert_eq!(
            input,
            vec![
                Record { items: vec![1, 2] },
                Record { items: vec![3, 4] },
                Record { items: vec![5] },
            ]
        );
    }
}

Assembly machine

This module provides a machine that can process assembly-like instructions. A machine consist of three parts:

• Instructions (must implement MachineInstruction)
• A register (must implement MachineRegister)
• An output receiver (must implement OutputReceiver)

When the machine is run, it will start executing the instructions one by one. Each instruction specifies what the next instruction is (usually the next line, but you can also jump to some other spot). As soon as the program counter reaches a non-existent instruction, the machine will halt. Instructions may use the register to keep track of values, and may use the output receiver to send output to some (imaginary) output device, such as an antenna. When running the machine, you also get to specify a pre-execute hook (PreExecuteHook). For each instructions, the machine will call this hook before actually executing it. This allows you to manipulate the normal flow of the program. For example:

• Apply optimizations
• Detect loops

To more easily parse instructions from your input file, this library provides:

• machine::instruction::Value - Represents either a raw value or a reference to a register.
• machine::instruction::ParsedMachineInstruction - Represents a single parsed line. Allows you to easily access to command (.get_command()) or specific arguments, which will be parsed to the correct type (.get_argument::<T>(idx)).

Example

use rdcl_aoc_helpers::error::ParseError;
use rdcl_aoc_helpers::machine::hook::NoopHook;
use rdcl_aoc_helpers::machine::instruction::{MachineInstruction, ParsedMachineInstruction, Value};
use rdcl_aoc_helpers::machine::output_receiver::OutputReceiver;
use rdcl_aoc_helpers::machine::register::MachineRegister;
use rdcl_aoc_helpers::machine::Machine;

fn main() {
    let instructions = parse_input().unwrap();
    let mut machine = Machine::new_simple_machine(&instructions);
    machine.run(&mut NoopHook::default());

    println!("Final register state: {}", machine.register);
}

fn parse_input() -> Result<Vec<Instruction>, ParseError> {
    /* ... */
}

enum Instruction {
    Add(Value, Value, char),
    Jump(i64),
}

impl MachineInstruction for Instruction {
    fn execute<R: MachineRegister, O: OutputReceiver<R>>(
        &self,
        register: &mut R,
        _output_receiver: &mut O,
    ) -> i64 {
        match self {
            Instruction::Add(v1, v2, reg) => {
                register.write(*reg, v1.get(register), v2.get(register));
                1
            }
            Instruction::Jump(by) => by,
        }
    }

    fn from_parsed_machine_instruction(
        parsed: &ParsedMachineInstruction,
    ) -> Result<Self, ParseError> {
        match parsed.get_command() {
            "add" => Ok(Instruction::Add(
                parsed.get_argument(0)?,
                parsed.get_argument(1)?,
                parsed.get_argument(2)?
            )),
            "jmp" => Ok(Instruction::Jump(
                parsed.get_argument(0)?
            )),
            _ => Err(ParseError(format!("Unknown command: {}", parsed))),
        }
    }
}

impl FromStr for Instruction {
    type Err = ParseError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        <Self as MachineInstruction>::from_str(s)
    }
}

Math

math::abs_diff & math::taxi_cab_*d

The function abs_diff computes the absolute difference between two points. The functions taxi_cab_*d (implemented for 2D, 3D and 4D) computes the taxi cab distance between two points.

Example

use rdcl_aoc_helpers::math::{abs_diff, taxi_cab_2d, taxi_cab_3d, taxi_cab_4d};

fn main() {
    println!("|1 - 5| = {}", abs_diff(1, 5));
    println!("|(1, 10) - (5, 3)| = {}", taxi_cab_2d((1, 10), (5, 3)));
    println!("|(1, 10, 2) - (5, 3, 4)| = {}", taxi_cab_3d((1, 10, 2), (5, 3, 4)));
    println!("|(1, 10, 2, 7) - (5, 3, 4, 2)| = {}", taxi_cab_4d((1, 10, 2, 7), (5, 3, 4, 2)));
}

math::gcd

Computes the greatest common divisor of two numbers.

Example

use rdcl_aoc_helpers::math::gcd;

fn main() {
    let a = 35;
    let b = 49;
    println!("gcd({}, {}) = {}", a, b, gcd(a, b));
}

math::lcm

Computes the least common multiple of two numbers.

Example

use rdcl_aoc_helpers::math::lcm;

fn main() {
    let a = 35;
    let b = 49;
    println!("lcm({}, {}) = {}", a, b, lcm(a, b));
}

math::solve_crt

Solve the chinese remainder theorem for (n1, a1) and (n2, a2). We assume that:

• n1 and n2 are coprime
• n1 and n2 are no more than 63 bits (as they are converted to i64)

Example

use rdcl_aoc_helpers::math::solve_crt;

fn main() {
    println!("solve_crt((3, 1), (5, 4)) = {}", solve_crt((3, 1), (5, 4)));
}

math::bezout_coefficients

Find t and s, such that ta + sb = gcd(p, q).

Example

use rdcl_aoc_helpers::math::bezout_coefficients;

fn main() {
    println!("bezout_coefficients(3, 4) = {}", bezout_coefficients(3, 4));
}

math::polynomial::Polynomial

Allows you to work with polynomials. Currently supported:

• Creating new polynomials (let y = Polynomial::new(&[1, -25, 5])).
• Formatting a polynomial in a human readable way (format!("{}", y)).
• Adding two polynomials together.
• Evaluating a polynomial at a point x (y.at(x)).
• Finding all roots of a polynomial (y.find_roots()).

To do:

• Implement more arithmetic operations (e.g. multiplication).
• Implement Fn(i64) -> i64 for polynomials, so you can call them (y(x), rather than y.at(x)).
• Either implement FromStr, or create a macro to more easily create polynomials (e.g. polynomial![x^2 - 25x + 5]).

Example

use rdcl_aoc_helpers::math::polynomial::Polynomial;

fn main() {
    let y1 = Polynomial::new(&[1, -25, 5]);
    println!("Solving {} = 0", y1);
    for x in y1.find_roots() {
        println!("For x = {}, y = {}.", x, y1.at(x));
    }
    let y2 = Polynomial::new(&[25, -5]);
    println!("({}) + ({}) = {}", y1, y2, y1 + y2);
}

Parts

part::Part

This enum is useful if you need to explicitly refer to a part. It implements str::FromStr and fmt::Display, so you can easily convert to and from a string.

Example

use rdcl_aoc_helpers::part::Part;

fn main() {
    let part = "part 1".parse::<Part>().unwrap();
    println!("[{}] ...", part); // outputs "[part 1] ..."

    let part = Part::Two;
    println!("[{}] ...", part); // outputs "[part 2] ..."
}

Permutations

permutations::Permutations

Produce all permutations of a given collection.

Example

use rdcl_aoc_helpers::permutations::Permutations;

fn main() {
    for permutation in (0..5).collect::<Permutations<u8>>() {
        println!("{:?}", permutation);
    }
}

Search

search::Navigable

Implement this trait to be able to use A* to find the shortest path between two points.