this post was submitted on 04 Dec 2024
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Advent Of Code

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An unofficial home for the advent of code community on programming.dev! Other challenges are also welcome!

Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.

Everybody Codes is another collection of programming puzzles with seasonal events.

EC 2025

AoC 2025

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console.log('Hello World')

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Day 4: Ceres Search

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[โ€“] sleeplessone@lemmy.ml -1 points 11 months ago

Rust

I'm a day behind on this one due to a lot of work with my job and school.

use std::iter::zip;

use crate::utils::read_lines;

pub fn solution1() {
    let puzzle = read_puzzle();

    let horizontal_sum = puzzle
        .iter()
        .map(|line| {
            line.windows(4)
                .filter(|window| {
                    matches!(window, [b'X', b'M', b'A', b'S'] | [b'S', b'A', b'M', b'X'])
                })
                .count() as u32
        })
        .sum::<u32>();
    let vertical_and_diagonal_sum = puzzle
        .windows(4)
        .map(|window| {
            count_xmas(window, (0, 0, 0, 0))
                + count_xmas(window, (0, 1, 2, 3))
                + count_xmas(window, (3, 2, 1, 0))
        })
        .sum::<u32>();

    println!(
        "XMAS count = {}",
        horizontal_sum + vertical_and_diagonal_sum
    );
}

pub fn solution2() {
    let puzzle = read_puzzle();

    let sum = puzzle
        .windows(3)
        .map(|window| {
            zip(
                window[0].windows(3),
                zip(window[1].windows(3), window[2].windows(3)),
            )
            .map(|(a, (b, c))| (a, b, c))
            .filter(|tuple| {
                matches!(
                    tuple,
                    ([b'M', _, b'M'], [_, b'A', _], [b'S', _, b'S'])
                        | ([b'S', _, b'M'], [_, b'A', _], [b'S', _, b'M'])
                        | ([b'M', _, b'S'], [_, b'A', _], [b'M', _, b'S'])
                        | ([b'S', _, b'S'], [_, b'A', _], [b'M', _, b'M'])
                )
            })
            .count() as u32
        })
        .sum::<u32>();

    println!("X-MAS count = {sum}");
}

fn count_xmas(
    window: &[Vec<u8>],
    (skip0, skip1, skip2, skip3): (usize, usize, usize, usize),
) -> u32 {
    zip(
        window[0].iter().skip(skip0),
        zip(
            window[1].iter().skip(skip1),
            zip(window[2].iter().skip(skip2), window[3].iter().skip(skip3)),
        ),
    )
    .map(|(a, (b, (c, d)))| (a, b, c, d))
    .filter(|tup| matches!(tup, (b'X', b'M', b'A', b'S') | (b'S', b'A', b'M', b'X')))
    .count() as u32
}

fn read_puzzle() -> Vec<Vec<u8>> {
    read_lines("src/day4/input.txt")
        .map(|line| line.into_bytes())
        .collect()
}

The standard library windows method and pattern matching have been carrying me this year so far.