2021: day11: part 1 & 2
This commit is contained in:
parent
8ddde41f0c
commit
1d6ed92b36
10
aoc2021/input/day11.txt
Normal file
10
aoc2021/input/day11.txt
Normal file
|
@ -0,0 +1,10 @@
|
||||||
|
4764745784
|
||||||
|
4643457176
|
||||||
|
8322628477
|
||||||
|
7617152546
|
||||||
|
6137518165
|
||||||
|
1556723176
|
||||||
|
2187861886
|
||||||
|
2553422625
|
||||||
|
4817584638
|
||||||
|
3754285662
|
10
aoc2021/input/day11_provided.txt
Normal file
10
aoc2021/input/day11_provided.txt
Normal file
|
@ -0,0 +1,10 @@
|
||||||
|
5483143223
|
||||||
|
2745854711
|
||||||
|
5264556173
|
||||||
|
6141336146
|
||||||
|
6357385478
|
||||||
|
4167524645
|
||||||
|
2176841721
|
||||||
|
6882881134
|
||||||
|
4846848554
|
||||||
|
5283751526
|
236
aoc2021/src/day11.rs
Normal file
236
aoc2021/src/day11.rs
Normal file
|
@ -0,0 +1,236 @@
|
||||||
|
use std::fmt::Write;
|
||||||
|
|
||||||
|
use anyhow::{Context, Result};
|
||||||
|
|
||||||
|
const INPUT: &str = include_str!("../input/day11.txt");
|
||||||
|
|
||||||
|
pub fn run() -> Result<String> {
|
||||||
|
let mut res = String::with_capacity(128);
|
||||||
|
|
||||||
|
writeln!(res, "part 1: {}", part1(INPUT)?)?;
|
||||||
|
writeln!(res, "part 2: {}", part2(INPUT)?)?;
|
||||||
|
|
||||||
|
Ok(res)
|
||||||
|
}
|
||||||
|
|
||||||
|
fn part1(input: &str) -> Result<usize> {
|
||||||
|
let mut grid: OctopusGrid = input.parse()?;
|
||||||
|
|
||||||
|
Ok((0..100).map(|_| grid.step()).sum())
|
||||||
|
}
|
||||||
|
|
||||||
|
fn part2(input: &str) -> Result<usize> {
|
||||||
|
let mut grid: OctopusGrid = input.parse()?;
|
||||||
|
|
||||||
|
let (_, step) = (0..)
|
||||||
|
.map(|step| (grid.step(), step))
|
||||||
|
.find(|(flashes, _)| *flashes == 100)
|
||||||
|
.context("never reached step where octopuses all flashed simultaneously")?;
|
||||||
|
|
||||||
|
Ok(step + 1)
|
||||||
|
}
|
||||||
|
|
||||||
|
#[derive(Clone, Copy, Debug)]
|
||||||
|
struct Octopus {
|
||||||
|
energy_level: u8,
|
||||||
|
has_flashed: bool,
|
||||||
|
}
|
||||||
|
|
||||||
|
impl Octopus {
|
||||||
|
fn increment_energy_level(&mut self) {
|
||||||
|
self.energy_level += 1;
|
||||||
|
}
|
||||||
|
|
||||||
|
fn reset_energy_level(&mut self) {
|
||||||
|
if self.has_flashed {
|
||||||
|
self.energy_level = 0;
|
||||||
|
self.has_flashed = false;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
fn flashes(&mut self) -> bool {
|
||||||
|
if self.energy_level > 9 && !self.has_flashed {
|
||||||
|
self.has_flashed = true;
|
||||||
|
return true;
|
||||||
|
}
|
||||||
|
|
||||||
|
false
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
impl TryFrom<char> for Octopus {
|
||||||
|
type Error = anyhow::Error;
|
||||||
|
|
||||||
|
fn try_from(value: char) -> Result<Self> {
|
||||||
|
Ok(Octopus {
|
||||||
|
energy_level: value
|
||||||
|
.to_digit(10)
|
||||||
|
.with_context(|| format!("couldn't convert char `{}` to digit", value))?
|
||||||
|
as u8,
|
||||||
|
has_flashed: false,
|
||||||
|
})
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
#[derive(Clone, Copy)]
|
||||||
|
enum Neighbour {
|
||||||
|
Up,
|
||||||
|
Down,
|
||||||
|
Left,
|
||||||
|
Right,
|
||||||
|
UpperLeft,
|
||||||
|
UpperRight,
|
||||||
|
LowerLeft,
|
||||||
|
LowerRight,
|
||||||
|
}
|
||||||
|
|
||||||
|
impl Neighbour {
|
||||||
|
fn apply(&self, x: usize, y: usize, width: usize, height: usize) -> Option<(usize, usize)> {
|
||||||
|
match self {
|
||||||
|
Neighbour::Left if x > 0 => Some((x - 1, y)),
|
||||||
|
Neighbour::Right if x < width - 1 => Some((x + 1, y)),
|
||||||
|
Neighbour::Up if y > 0 => Some((x, y - 1)),
|
||||||
|
Neighbour::Down if y < height - 1 => Some((x, y + 1)),
|
||||||
|
Neighbour::UpperLeft => Neighbour::Left
|
||||||
|
.apply(x, y, width, height)
|
||||||
|
.and_then(|(x, y)| Neighbour::Up.apply(x, y, width, height)),
|
||||||
|
Neighbour::UpperRight => Neighbour::Right
|
||||||
|
.apply(x, y, width, height)
|
||||||
|
.and_then(|(x, y)| Neighbour::Up.apply(x, y, width, height)),
|
||||||
|
Neighbour::LowerLeft => Neighbour::Left
|
||||||
|
.apply(x, y, width, height)
|
||||||
|
.and_then(|(x, y)| Neighbour::Down.apply(x, y, width, height)),
|
||||||
|
Neighbour::LowerRight => Neighbour::Right
|
||||||
|
.apply(x, y, width, height)
|
||||||
|
.and_then(|(x, y)| Neighbour::Down.apply(x, y, width, height)),
|
||||||
|
_ => None,
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
const ALL: &'static [Self] = &[
|
||||||
|
Neighbour::Left,
|
||||||
|
Neighbour::Right,
|
||||||
|
Neighbour::Up,
|
||||||
|
Neighbour::Down,
|
||||||
|
Neighbour::UpperLeft,
|
||||||
|
Neighbour::UpperRight,
|
||||||
|
Neighbour::LowerLeft,
|
||||||
|
Neighbour::LowerRight,
|
||||||
|
];
|
||||||
|
}
|
||||||
|
|
||||||
|
#[derive(Debug)]
|
||||||
|
struct OctopusGrid {
|
||||||
|
octopuses: Vec<Octopus>,
|
||||||
|
width: usize,
|
||||||
|
height: usize,
|
||||||
|
}
|
||||||
|
|
||||||
|
impl OctopusGrid {
|
||||||
|
fn neighbours(&self, x: usize, y: usize) -> impl Iterator<Item = (usize, usize)> + 'static {
|
||||||
|
let width = self.width;
|
||||||
|
let height = self.height;
|
||||||
|
Neighbour::ALL
|
||||||
|
.iter()
|
||||||
|
.copied()
|
||||||
|
.filter_map(move |neighbour| neighbour.apply(x, y, width, height))
|
||||||
|
}
|
||||||
|
|
||||||
|
fn get_mut(&mut self, x: usize, y: usize) -> &mut Octopus {
|
||||||
|
&mut self.octopuses[y * self.width + x]
|
||||||
|
}
|
||||||
|
|
||||||
|
fn step(&mut self) -> usize {
|
||||||
|
// First, the energy level of each octopus increases by 1.
|
||||||
|
self.octopuses
|
||||||
|
.iter_mut()
|
||||||
|
.for_each(Octopus::increment_energy_level);
|
||||||
|
|
||||||
|
// Then, any octopus with an energy level greater than 9 flashes. This increases the energy
|
||||||
|
// level of all adjacent octopuses by 1, including octopuses that are diagonally adjacent.
|
||||||
|
// If this causes an octopus to have an energy level greater than 9, it also flashes. This
|
||||||
|
// process continues as long as new octopuses keep having their energy level increased
|
||||||
|
// beyond 9. (An octopus can only flash at most once per step.)
|
||||||
|
let mut flashed = true;
|
||||||
|
let mut flashes = 0;
|
||||||
|
while flashed {
|
||||||
|
flashed = false;
|
||||||
|
for index in 0..self.octopuses.len() {
|
||||||
|
if self.octopuses[index].flashes() {
|
||||||
|
let (x, y) = (index % self.width, index / self.width);
|
||||||
|
for (x, y) in self.neighbours(x, y) {
|
||||||
|
self.get_mut(x, y).increment_energy_level();
|
||||||
|
}
|
||||||
|
|
||||||
|
flashed = true;
|
||||||
|
flashes += 1;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
// Finally, any octopus that flashed during this step has its energy level set to 0, as it
|
||||||
|
// used all of its energy to flash.
|
||||||
|
self.octopuses
|
||||||
|
.iter_mut()
|
||||||
|
.for_each(Octopus::reset_energy_level);
|
||||||
|
|
||||||
|
flashes
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
impl std::str::FromStr for OctopusGrid {
|
||||||
|
type Err = anyhow::Error;
|
||||||
|
|
||||||
|
fn from_str(s: &str) -> Result<Self, Self::Err> {
|
||||||
|
let mut octopuses = Vec::new();
|
||||||
|
|
||||||
|
let mut height = 0;
|
||||||
|
let mut width = None;
|
||||||
|
for line in s.lines().map(str::trim) {
|
||||||
|
let octopus_line = line
|
||||||
|
.chars()
|
||||||
|
.map(TryFrom::try_from)
|
||||||
|
.collect::<Result<Vec<_>>>()?;
|
||||||
|
|
||||||
|
if width.is_none() {
|
||||||
|
width = Some(octopus_line.len());
|
||||||
|
}
|
||||||
|
|
||||||
|
height += 1;
|
||||||
|
octopuses.extend_from_slice(&octopus_line);
|
||||||
|
}
|
||||||
|
|
||||||
|
Ok(OctopusGrid {
|
||||||
|
octopuses,
|
||||||
|
width: width.context("0 lines parsed, width never computed")?,
|
||||||
|
height,
|
||||||
|
})
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
#[cfg(test)]
|
||||||
|
mod tests {
|
||||||
|
use super::*;
|
||||||
|
|
||||||
|
const PROVIDED: &str = include_str!("../input/day11_provided.txt");
|
||||||
|
|
||||||
|
#[test]
|
||||||
|
fn part1_provided() {
|
||||||
|
assert_eq!(part1(PROVIDED).unwrap(), 1656);
|
||||||
|
}
|
||||||
|
|
||||||
|
#[test]
|
||||||
|
fn part1_real() {
|
||||||
|
assert_eq!(part1(INPUT).unwrap(), 1588);
|
||||||
|
}
|
||||||
|
|
||||||
|
#[test]
|
||||||
|
fn part2_provided() {
|
||||||
|
assert_eq!(part2(PROVIDED).unwrap(), 195);
|
||||||
|
}
|
||||||
|
|
||||||
|
#[test]
|
||||||
|
fn part2_real() {
|
||||||
|
assert_eq!(part2(INPUT).unwrap(), 517);
|
||||||
|
}
|
||||||
|
}
|
|
@ -10,3 +10,4 @@ pub mod day07;
|
||||||
pub mod day08;
|
pub mod day08;
|
||||||
pub mod day09;
|
pub mod day09;
|
||||||
pub mod day10;
|
pub mod day10;
|
||||||
|
pub mod day11;
|
||||||
|
|
|
@ -12,6 +12,7 @@ use aoc2021::day07;
|
||||||
use aoc2021::day08;
|
use aoc2021::day08;
|
||||||
use aoc2021::day09;
|
use aoc2021::day09;
|
||||||
use aoc2021::day10;
|
use aoc2021::day10;
|
||||||
|
use aoc2021::day11;
|
||||||
|
|
||||||
fn main() -> Result<()> {
|
fn main() -> Result<()> {
|
||||||
let days: &[DayFunc] = &[
|
let days: &[DayFunc] = &[
|
||||||
|
@ -25,6 +26,7 @@ fn main() -> Result<()> {
|
||||||
day08::run,
|
day08::run,
|
||||||
day09::run,
|
day09::run,
|
||||||
day10::run,
|
day10::run,
|
||||||
|
day11::run,
|
||||||
];
|
];
|
||||||
|
|
||||||
aoc::run(days)
|
aoc::run(days)
|
||||||
|
|
Loading…
Reference in a new issue