advent-2022-rust/src/days/day18/mod.rs

use itertools::Itertools;
use std::{collections::HashSet, num::ParseIntError};
use thiserror::Error;

use crate::common::file::split_lines;

use super::template::{DayTrait, ResultType};

const DAY_NUMBER: usize = 18;

pub struct Day;

impl DayTrait for Day {
    fn get_day_number(&self) -> usize {
        DAY_NUMBER
    }

    fn part1(&self, lines: &str) -> anyhow::Result<ResultType> {
        let blob = Blob::try_from(lines)?;
        Ok(ResultType::Integer(blob.count_sides()))
    }

    fn part2(&self, lines: &str) -> anyhow::Result<ResultType> {
        let blob = Blob::try_from(lines)?;
        Ok(ResultType::Integer(blob.count_outside()))
    }
}

#[derive(Debug, Error)]
enum DropletError {
    #[error("Illegal Droplet: {0}")]
    IllegalDroplet(String),

    #[error("no Integer")]
    NoInteger(#[from] ParseIntError),
}

#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
struct Droplet(i64, i64, i64);

impl Droplet {
    fn parse(line: &str) -> Result<Droplet, DropletError> {
        let split = line.split(",").collect_vec();
        if split.len() != 3 {
            return Err(DropletError::IllegalDroplet(line.to_owned()));
        }
        let (x, y, z) = (split[0].parse()?, split[1].parse()?, split[2].parse()?);
        Ok(Droplet(x, y, z))
    }
    pub fn neighbors(&self) -> Neighbors<'_> {
        Neighbors::new(self)
    }
}

struct Neighbors<'a>(&'a Droplet, usize);

impl<'a> Neighbors<'a> {
    pub fn new(droplet: &'a Droplet) -> Neighbors<'a> {
        Neighbors(droplet, 0)
    }
}

impl<'a> Iterator for Neighbors<'a> {
    type Item = Droplet;

    fn next(&mut self) -> Option<Self::Item> {
        self.1 += 1;
        match self.1 {
            1 => Some(Droplet(self.0 .0 - 1, self.0 .1, self.0 .2)),
            2 => Some(Droplet(self.0 .0 + 1, self.0 .1, self.0 .2)),
            3 => Some(Droplet(self.0 .0, self.0 .1 - 1, self.0 .2)),
            4 => Some(Droplet(self.0 .0, self.0 .1 + 1, self.0 .2)),
            5 => Some(Droplet(self.0 .0, self.0 .1, self.0 .2 - 1)),
            6 => Some(Droplet(self.0 .0, self.0 .1, self.0 .2 + 1)),
            _ => None,
        }
    }
}

struct Ranges {
    x: (i64, i64),
    y: (i64, i64),
    z: (i64, i64),
}

impl Ranges {
    pub fn new(droplet: &Droplet) -> Self {
        Ranges {
            x: (droplet.0, droplet.0),
            y: (droplet.1, droplet.1),
            z: (droplet.2, droplet.2),
        }
    }

    pub fn contains(&self, droplet: &Droplet) -> bool {
        self.x.0 <= droplet.0
            && droplet.0 <= self.x.1
            && self.y.0 <= droplet.1
            && droplet.1 <= self.y.1
            && self.z.0 <= droplet.2
            && droplet.2 <= self.z.1
    }

    pub fn grow(&mut self) {
        self.x.0 -= 1;
        self.x.1 += 1;
        self.y.0 -= 1;
        self.y.1 += 1;
        self.z.0 -= 1;
        self.z.1 += 1;
    }

    pub fn first(&self) -> Droplet {
        Droplet(self.x.0, self.y.0, self.z.0)
    }

    pub fn extend(&mut self, droplet: &Droplet) {
        self.x.0 = self.x.0.min(droplet.0);
        self.x.1 = self.x.1.max(droplet.0);
        self.y.0 = self.y.0.min(droplet.1);
        self.y.1 = self.y.1.max(droplet.1);
        self.z.0 = self.z.0.min(droplet.2);
        self.z.1 = self.z.1.max(droplet.2);
    }

    #[allow(dead_code)]
    pub fn volume(&self) -> i64 {
        (self.x.1 - self.x.0 + 1) * (self.y.1 - self.y.0 + 1) * (self.z.1 - self.z.0 + 1)
    }
}

struct Blob {
    droplets: HashSet<Droplet>,
}

impl TryFrom<&str> for Blob {
    type Error = DropletError;

    fn try_from(lines: &str) -> Result<Self, Self::Error> {
        let droplets = split_lines(lines)
            .map(|line| Droplet::parse(line))
            .try_collect()?;
        Ok(Blob { droplets })
    }
}

impl Blob {
    fn extent(&self) -> Option<Ranges> {
        if self.droplets.is_empty() {
            return None;
        }

        let mut range = Ranges::new(&self.droplets.iter().next().unwrap());
        for droplet in self.droplets.iter().skip(1) {
            range.extend(droplet);
        }
        Some(range)
    }

    pub fn count_sides(&self) -> i64 {
        let mut sides = 0;
        let mut known = HashSet::new();
        for droplet in &self.droplets {
            sides += 6;
            for neighbor in droplet.neighbors() {
                if known.contains(&neighbor) {
                    sides -= 2;
                }
            }
            known.insert(droplet);
        }
        sides
    }

    pub fn count_outside(&self) -> i64 {
        let Some(mut extent)= self.extent() else {
            return 0;
        };
        let mut sides = 0;

        extent.grow();

        let mut outer = HashSet::new();
        let mut queue = Vec::new();
        queue.push(extent.first());
        while let Some(next) = queue.pop() {
            for neighbor in next.neighbors() {
                if extent.contains(&neighbor) && !outer.contains(&neighbor) {
                    if self.droplets.contains(&neighbor) {
                        sides += 1;
                    } else if !queue.contains(&neighbor) {
                        queue.push(neighbor);
                    }
                }
            }
            outer.insert(next);
        }

        sides
    }
}

#[cfg(test)]
mod test {
    use super::*;
    use crate::common::file::read_string;
    use anyhow::Result;

    #[test]
    fn test_part1() -> Result<()> {
        let day = Day {};
        let lines = read_string(day.get_day_number(), "example01.txt")?;
        let expected = ResultType::Integer(64);
        let result = day.part1(&lines)?;
        assert_eq!(result, expected);

        Ok(())
    }

    #[test]
    fn test_part2() -> Result<()> {
        let day = Day {};
        let lines = read_string(day.get_day_number(), "example01.txt")?;
        let expected = ResultType::Integer(58);
        let result = day.part2(&lines)?;
        assert_eq!(result, expected);

        Ok(())
    }

    #[test]
    fn parse() -> Result<()> {
        let input = "1,2,3";
        let expected = Droplet(1, 2, 3);
        let result = Droplet::parse(input)?;
        assert_eq!(result, expected);

        Ok(())
    }

    #[test]
    fn neighbors() {
        let droplet = Droplet(1, 1, 1);
        let expected = vec![
            Droplet(0, 1, 1),
            Droplet(2, 1, 1),
            Droplet(1, 0, 1),
            Droplet(1, 2, 1),
            Droplet(1, 1, 0),
            Droplet(1, 1, 2),
        ];
        assert_eq!(droplet.neighbors().collect_vec(), expected);
    }

    #[test]
    fn simple() {
        let blob = Blob {
            droplets: HashSet::from_iter(vec![Droplet(1, 1, 1), Droplet(1, 1, 2)]),
        };
        assert_eq!(blob.count_sides(), 10);
    }
}