Day 12
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@ -0,0 +1,129 @@
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use crate::util::maps::*;
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const DISCOUNT: bool = true;
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pub fn day12() {
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let mut plots: Map<char> = Map::from_string(&crate::input(12));
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let mut regions: Vec<Region> = vec![];
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for (x, y) in plots.coordinates() {
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if plots.get(x, y) != Some('.') {
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let region = Region::new(x, y, &plots);
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for (x, y) in plots.coordinates() {
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if region.tiles.get(x, y).unwrap() {
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plots.set(x, y, '.');
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}
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}
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regions.push(region);
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}
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}
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let mut total_cost: u64 = 0;
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for region in regions {
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let mut sides: u64 = 0;
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let mut borders = region.borders.clone();
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while let Some(border) = borders.pop() {
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let mut combined = vec![border];
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while let Some(pos) = borders
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.iter()
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.position(|other| combined.iter().any(|b| b.contiguous_straight(other)))
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{
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combined.push(borders.remove(pos));
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}
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sides += 1;
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}
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let area = region.tiles.iter().filter(|&&t| t).count() as u64;
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total_cost += if DISCOUNT {
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area * sides
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} else {
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area * region.borders.len() as u64
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};
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}
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println!("Total Cost: {}", total_cost);
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}
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#[derive(PartialEq, Eq, Clone)]
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struct Border {
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x: u64,
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y: u64,
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facing: Direction,
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}
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impl Border {
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fn new(x: u64, y: u64, facing: Direction) -> Self {
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Self { x, y, facing }
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}
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fn contiguous_straight(&self, other: &Self) -> bool {
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if self.facing != other.facing {
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return false;
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}
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if self.facing == Direction::North || self.facing == Direction::South {
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return self.y == other.y && self.x.max(other.x) - self.x.min(other.x) == 1;
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}
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if self.facing == Direction::West || self.facing == Direction::East {
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return self.x == other.x && self.y.max(other.y) - self.y.min(other.y) == 1;
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}
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unreachable!();
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}
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}
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struct Region {
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pub borders: Vec<Border>,
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pub tiles: Map<bool>,
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}
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impl Region {
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fn new(x: usize, y: usize, plots: &Map<char>) -> Self {
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let c = plots.get(x, y).unwrap();
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let mut tiles = Map::<bool>::from_dimensions(plots.width(), plots.height(), false);
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fn collect_plots(
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c: char,
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x: usize,
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y: usize,
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plots: &Map<char>,
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tiles: &mut Map<bool>,
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) -> Vec<(usize, usize)> {
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if plots.get(x, y) != Some(c) || tiles.get(x, y) == Some(true) {
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return vec![];
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}
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tiles.set(x, y, true);
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let mut region = vec![(x, y)];
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for (nx, ny) in Direction::all_variants()
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.into_iter()
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.filter_map(|d| plots.travel(x, y, d))
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{
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region.extend(collect_plots(c, nx, ny, plots, tiles));
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}
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region
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}
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let collected_plots = collect_plots(c, x, y, plots, &mut tiles);
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let borders = collected_plots
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.iter()
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.flat_map(|&(x, y)| {
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Direction::all_variants().into_iter().filter_map(move |d| {
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match plots.travel_get(x, y, d) {
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Some(o) if o == c => None,
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_ => Some(Border::new(x as u64, y as u64, d)),
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}
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})
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})
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.collect();
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Self { borders, tiles }
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}
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}
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@ -1,3 +1,5 @@
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pub mod util;
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#[allow(dead_code)]
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mod day1;
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#[allow(dead_code)]
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@ -18,10 +20,12 @@ mod day8;
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mod day9;
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#[allow(dead_code)]
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mod day10;
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#[allow(dead_code)]
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mod day11;
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mod day12;
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fn main() {
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day11::day11();
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day12::day12();
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}
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pub fn input(day: u8) -> String {
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@ -0,0 +1 @@
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pub mod maps;
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@ -0,0 +1,108 @@
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use itertools::Itertools;
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#[derive(Copy, Clone, PartialEq, Eq)]
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pub enum Direction {
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North,
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South,
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East,
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West,
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}
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impl Direction {
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pub fn all_variants() -> Vec<Self> {
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vec![Self::North, Self::East, Self::West, Self::South]
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}
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}
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#[derive(Clone)]
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pub struct Map<T>
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where
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T: Copy,
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{
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pub map: Vec<Vec<T>>,
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}
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impl Map<char> {
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pub fn from_string(string: &str) -> Self {
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Map::from_2d_vec(
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string
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.lines()
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.filter(|line| !line.is_empty())
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.map(|line| line.chars().collect())
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.collect(),
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)
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}
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}
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impl<T> Map<T>
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where
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T: Copy,
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{
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pub fn from_2d_vec(map: Vec<Vec<T>>) -> Self {
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Self { map }
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}
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pub fn from_dimensions(width: usize, height: usize, default: T) -> Self {
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Self {
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map: vec![vec![default; width]; height],
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}
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}
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pub fn travel(&self, x: usize, y: usize, direction: Direction) -> Option<(usize, usize)> {
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match direction {
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Direction::North => Some((x, y.checked_sub(1)?)),
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Direction::South => {
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if y + 1 < self.height() {
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Some((x, y + 1))
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} else {
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None
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}
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}
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Direction::West => Some((x.checked_sub(1)?, y)),
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Direction::East => {
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if x + 1 < self.width() {
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Some((x + 1, y))
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} else {
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None
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}
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}
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}
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}
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pub fn travel_get(&self, x: usize, y: usize, direction: Direction) -> Option<T> {
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let (nx, ny) = self.travel(x, y, direction)?;
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self.get(nx, ny)
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}
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pub fn get(&self, x: usize, y: usize) -> Option<T> {
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Some(*self.map.get(y)?.get(x)?)
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}
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pub fn set(&mut self, x: usize, y: usize, value: T) {
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self.map[y][x] = value
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}
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pub fn height(&self) -> usize {
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self.map.len()
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}
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pub fn width(&self) -> usize {
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self.map[0].len()
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}
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pub fn in_bounds(&self, x: usize, y: usize) -> bool {
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x < self.width() && y < self.height()
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}
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pub fn iter(&self) -> impl Iterator<Item = &T> {
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self.map.iter().flat_map(|row| row.iter())
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}
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pub fn coordinates(&self) -> impl Iterator<Item = (usize, usize)> {
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(0..self.width()).cartesian_product(0..self.height())
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}
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pub fn enumerate(&self) -> impl Iterator<Item = (usize, usize, &T)> {
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self.coordinates().map(|(x, y)| (x, y, &self.map[y][x]))
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}
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}
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