Day 2: Cube Conundrum

Megathread guidelines

  • Keep top level comments as only solutions, if you want to say something other than a solution put it in a new post. (replies to comments can be whatever)
  • Code block support is not fully rolled out yet but likely will be in the middle of the event. Try to share solutions as both code blocks and using something such as https://topaz.github.io/paste/ or pastebin (code blocks to future proof it for when 0.19 comes out and since code blocks currently function in some apps and some instances as well if they are running a 0.19 beta)

FAQ

🔒This post will be unlocked when there is a decent amount of submissions on the leaderboard to avoid cheating for top spots

🔓 Edit: Post has been unlocked after 6 minutes

  • @CannotSleep420English
    2•6 months ago

    I’m a bit late to the party for day 2. Here’s my answer:

    use std::rc::Rc;

use crate::utils::read_lines;

#[derive(Clone, Copy, PartialEq, Eq)]
enum Cube {
    Red(usize),
    Green(usize),
    Blue(usize),
}

#[derive(Clone, Copy, PartialEq, Eq)]
struct Bag {
    pub red: usize,
    pub green: usize,
    pub blue: usize,
}

fn parse_num<'a, I>(mut group: I) -> usize
where
    I: Iterator,
{
    group
        .next()
        .expect("Should be number")
        .parse::()
        .expect("Should be number")
}

fn process_lines() -> impl Iterator> {
    read_lines("src/day_2/input.txt")
        .expect("Could not read file")
        .map(|line| {
            let line = line.expect("Should be line");
            (&line[(line.find(':').unwrap() + 1)..])
                .split(';')
                .flat_map(|section| section.split(","))
                .map(|group| {
                    let mut group = group.trim().split(' ');

                    match group.next_back().expect("Should be color") {
                        "red" => Cube::Red(parse_num(group)),
                        "green" => Cube::Green(parse_num(group)),
                        "blue" => Cube::Blue(parse_num(group)),
                        c @ _ => panic!("Color {c} not recognized"),
                    }
                })
                .collect::>()
        })
        .into_iter()
}

pub fn solution_1() {
    let bag = Bag {
        red: 12,
        green: 13,
        blue: 14,
    };
    let sum: usize = process_lines()
        .enumerate()
        .map(|(i, line)| {
            let is_possible = line.iter().all(|cube| match cube {
                Cube::Red(c) => *c <= bag.red,
                Cube::Green(c) => *c <= bag.green,
                Cube::Blue(c) => *c <= bag.blue,
            });

            if is_possible {
                i + 1
            } else {
                0
            }
        })
        .sum();

    println!("{sum}");
}

pub fn solution_2() {
    let powersum: usize = process_lines()
        .map(|line| {
            let bag = line.iter().fold(
                Bag {
                    red: 0,
                    blue: 0,
                    green: 0,
                },
                |mut bag, cube| {
                    match *cube {
                        Cube::Red(n) => {
                            if n > bag.red {
                                bag.red = n;
                            }
                        }
                        Cube::Green(n) => {
                            if n > bag.green {
                                bag.green = n;
                            }
                        }
                        Cube::Blue(n) => {
                            if n > bag.blue {
                                bag.blue = n;
                            }
                        }
                    }

                    bag
                },
            );

            bag.red * bag.blue * bag.green
        })
        .sum();

    println!("{powersum}");
}