Rust

Kinda sorta got day 5 done on time.

use std::cmp::Ordering;

use crate::utils::{bytes_to_num, read_lines};

pub fn solution1() {
    let mut lines = read_input();
    let rules = parse_rules(&mut lines);

    let middle_rules_sum = lines
        .filter_map(|line| {
            let line_nums = rule_line_to_list(&line);
            line_nums
                .is_sorted_by(|&a, &b| is_sorted(&rules, (a, b)))
                .then_some(line_nums[line_nums.len() / 2])
        })
        .sum::<usize>();

    println!("Sum of in-order middle rules = {middle_rules_sum}");
}

pub fn solution2() {
    let mut lines = read_input();
    let rules = parse_rules(&mut lines);

    let middle_rules_sum = lines
        .filter_map(|line| {
            let mut line_nums = rule_line_to_list(&line);

            (!line_nums.is_sorted_by(|&a, &b| is_sorted(&rules, (a, b)))).then(|| {
                line_nums.sort_by(|&a, &b| {
                    is_sorted(&rules, (a, b))
                        .then_some(Ordering::Less)
                        .unwrap_or(Ordering::Greater)
                });

                line_nums[line_nums.len() / 2]
            })
        })
        .sum::<usize>();

    println!("Sum of middle rules = {middle_rules_sum}");
}

fn read_input() -> impl Iterator<Item = String> {
    read_lines("src/day5/input.txt")
}

fn parse_rules(lines: &mut impl Iterator<Item = String>) -> Vec<(usize, usize)> {
    lines
        .take_while(|line| !line.is_empty())
        .fold(Vec::new(), |mut rules, line| {
            let (a, b) = line.as_bytes().split_at(2);
            let a = bytes_to_num(a);
            let b = bytes_to_num(&b[1..]);

            rules.push((a, b));

            rules
        })
}

fn rule_line_to_list(line: &str) -> Vec<usize> {
    line.split(',')
        .map(|s| bytes_to_num(s.as_bytes()))
        .collect::<Vec<_>>()
}

fn is_sorted(rules: &[(usize, usize)], tuple: (usize, usize)) -> bool {
    rules.iter().any(|&r| r == tuple)
}

Reusing my bytes_to_num function from day 3 feels nice. Pretty fun challenge.

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.

Rust

use crate::utils::read_lines;

pub fn solution1() {
    let lines = read_lines("src/day3/input.txt");
    let sum = lines
        .map(|line| {
            let mut sum = 0;
            let mut command_bytes = Vec::new();
            for byte in line.bytes() {
                match (byte, command_bytes.as_slice()) {
                    (b')', [.., b'0'..=b'9']) => {
                        handle_mul(&mut command_bytes, &mut sum);
                    }
                    _ if matches_mul(byte, &command_bytes) => {
                        command_bytes.push(byte);
                    }
                    _ => {
                        command_bytes.clear();
                    }
                }
            }

            sum
        })
        .sum::<usize>();

    println!("Sum of multiplication results = {sum}");
}

pub fn solution2() {
    let lines = read_lines("src/day3/input.txt");

    let mut can_mul = true;
    let sum = lines
        .map(|line| {
            let mut sum = 0;
            let mut command_bytes = Vec::new();
            for byte in line.bytes() {
                match (byte, command_bytes.as_slice()) {
                    (b')', [.., b'0'..=b'9']) if can_mul => {
                        handle_mul(&mut command_bytes, &mut sum);
                    }
                    (b')', [b'd', b'o', b'(']) => {
                        can_mul = true;
                        command_bytes.clear();
                    }
                    (b')', [.., b't', b'(']) => {
                        can_mul = false;
                        command_bytes.clear();
                    }
                    _ if matches_do_or_dont(byte, &command_bytes)
                        || matches_mul(byte, &command_bytes) =>
                    {
                        command_bytes.push(byte);
                    }
                    _ => {
                        command_bytes.clear();
                    }
                }
            }

            sum
        })
        .sum::<usize>();

    println!("Sum of enabled multiplication results = {sum}");
}

fn matches_mul(byte: u8, command_bytes: &[u8]) -> bool {
    matches!(
        (byte, command_bytes),
        (b'm', [])
            | (b'u', [.., b'm'])
            | (b'l', [.., b'u'])
            | (b'(', [.., b'l'])
            | (b'0'..=b'9', [.., b'(' | b'0'..=b'9' | b','])
            | (b',', [.., b'0'..=b'9'])
    )
}

fn matches_do_or_dont(byte: u8, command_bytes: &[u8]) -> bool {
    matches!(
        (byte, command_bytes),
        (b'd', [])
            | (b'o', [.., b'd'])
            | (b'n', [.., b'o'])
            | (b'\'', [.., b'n'])
            | (b'(', [.., b'o' | b't'])
            | (b't', [.., b'\''])
    )
}

fn handle_mul(command_bytes: &mut Vec<u8>, sum: &mut usize) {
    let first_num_index = command_bytes
        .iter()
        .position(u8::is_ascii_digit)
        .expect("Guarunteed to be there");
    let comma_index = command_bytes
        .iter()
        .position(|&c| c == b',')
        .expect("Guarunteed to be there.");

    let num1 = bytes_to_num(&command_bytes[first_num_index..comma_index]);
    let num2 = bytes_to_num(&command_bytes[comma_index + 1..]);

    *sum += num1 * num2;
    command_bytes.clear();
}

fn bytes_to_num(bytes: &[u8]) -> usize {
    bytes
        .iter()
        .rev()
        .enumerate()
        .map(|(i, digit)| (*digit - b'0') as usize * 10usize.pow(i as u32))
        .sum::<usize>()
}

Definitely not my prettiest code ever. It would probably look nicer if I used regex or some parsing library, but I took on the self-imposed challenge of not using third party libraries. Also, this is already further than I made it last year!

The is_sorted_by is a really nice approach. I originally tried using that function thinking that |a, b| a > b or |a, b| a < b would cut it but it didn’t end up working. I never thought to handle the check for the step being between 1 and 3 in the callback closure for that though.

Rust

use crate::utils::read_lines;

pub fn solution1() {
    let reports = get_reports();
    let safe_reports = reports
        .filter(|report| report.windows(3).all(window_is_valid))
        .count();

    println!("Number of safe reports = {safe_reports}");
}

pub fn solution2() {
    let reports = get_reports();
    let safe_reports = reports
        .filter(|report| {
            (0..report.len()).any(|i| {
                [&report[0..i], &report[i + 1..]]
                    .concat()
                    .windows(3)
                    .all(window_is_valid)
            })
        })
        .count();

    println!("Number of safe reports = {safe_reports}");
}

fn window_is_valid(window: &[usize]) -> bool {
    matches!(window[0].abs_diff(window[1]), 1..=3)
        && matches!(window[1].abs_diff(window[2]), 1..=3)
        && ((window[0] > window[1] && window[1] > window[2])
            || (window[0] < window[1] && window[1] < window[2]))
}

fn get_reports() -> impl Iterator<Item = Vec<usize>> {
    read_lines("src/day2/input.txt").map(|line| {
        line.split_ascii_whitespace()
            .map(|level| {
                level
                    .parse()
                    .expect("Reactor level is always valid integer")
            })
            .collect()
    })
}

Definitely trickier than yesterday’s. I feel like the windows solution isn’t the best, but it was what came to mind and ended up working for me.

Rust

I’m doing it in Rust again this year. I stopped keeping up with it after day 3 last year, so let’s hope I last longer this time around.

use std::collections::HashMap;

use crate::utils::read_lines;

pub fn solution1() {
    let (mut id_list1, mut id_list2) = get_id_lists();

    id_list1.sort();
    id_list2.sort();

    let total_distance = id_list1
        .into_iter()
        .zip(id_list2)
        .map(|(left, right)| (left - right).abs())
        .sum::<i32>();

    println!("Total distance = {total_distance}");
}

pub fn solution2() {
    let (id_list1, id_list2) = get_id_lists();

    let id_count_map = id_list2
        .into_iter()
        .fold(HashMap::<_, i32>::new(), |mut map, id| {
            *map.entry(id).or_default() += 1i32;

            map
        });

    let similarity_score = id_list1
        .into_iter()
        .map(|id| id * id_count_map.get(&id).copied().unwrap_or_default())
        .sum::<i32>();

    println!("Similarity score = {similarity_score}");
}

fn get_id_lists() -> (Vec<i32>, Vec<i32>) {
    read_lines("src/day1/input.txt")
        .map(|line| {
            let mut ids = line.split_whitespace().map(|id| {
                id.parse::<i32>()
                    .expect("Ids from input must be valid integers")
            });

            (
                ids.next().expect("First Id on line must be present"),
                ids.next().expect("Second Id on line must be present"),
            )
        })
        .unzip()
}

I’m keeping my solutions up on GitHub.

I rarely have access to one.

This meme makes it look like it’s hard decision. I always immediately slam the button on the right.

Blueprints I think.

“I think we’re in an age when nuclear deterrent is actually less effective because the West is very unlikely to use anything like a nuclear bomb, whereas our adversaries might,” he added. “Where you have technological parity but moral disparity, the actual disparity is much greater than people think.”

There’s a moral disparity alright, but it’s not the US who has the moral high ground.

Yeesh, I thought you were being hyperbolic, but it really is that bad! He even has this massive self report towards the end:

And how do you avoid being punished? There are two ways. One that works; and one that doesn’t. The one that doesn’t work is to design everything up front before coding. The one that does avoid the punishment is to override all the safeties.

And so you will declare all your classes and all your functions open. You will never use exceptions. And you will get used to using lots and lots of ! characters to override the null checks and allow NPEs to rampage through your systems.

Uncle Bob must be the kind of guy who makes all of his types any when writing Typescript.

At least it’s not XML.

It got stalled for awhile due to butting heads with a contributor who wanted to take the app in a direction that me and dessalines fundamentally disagreed with. At several points we overwrote each others’ changes in PRs. After having a PR that got held up for months due to these arguments, dessalines and I decided to keep moving forward without waiting for his input. After spending some time setting up an end to end testing framework, I’m now moving at a noticeably faster pace. Compare the difference in time between the PR being opened and it being merged from the argument filled PR listed earlier and the most recent feature PR.

You can write garbage code in rust, but the compiler will beat you with a stick for doing so.

I didn’t say otherwise. If anything, considering it’s 4chan we’re talking about, I expect it to be malicious.

The only PII the software itself stores are usernames, bcrypt hashes of passwords, JWT session tokens and, if the admin requires it or the user gives it voluntarily, emails. With this in mind, there are still important caveats to keep in mind.

First, there is no way to verify if a given instance is running a fork that collects more information than the upstream repo, not to mention any logging they might be doing. This is where Lemmy being self-hostable is a double-edged sword. On the one hand, if you have the sysadmin knowhow or know someone trustworthy who does, you can setup your own instance that you can be certain doesn’t collect any data you don’t expect it to. On the other hand, there is no way to prevent malicious actors from making compromised instances.

The other important caveat is that all posts and comments are public. Personal information you post in posts and comments can be used to identify you. This is true of all social media, even ones that don’t use usernames such as 4chan and similar chan-like image boards. No amount of software related privacy features can save you from bad opsec.

Opened an issue for you.

We’re waiting for Forgejo to support federation. We definitely want to move away from github, but we want to wait until we’re in a position for that move to be permanent while still making it easy for contributors to open issues and PRs.

Theres kbin, mbin, piefed, and sublinks.