Day 23, part 1
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19
src/bin/d23p1.rs
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19
src/bin/d23p1.rs
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use aoc22::{
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day23::{self, empty_ground},
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util,
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};
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const N_ROUNDS: usize = 10;
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pub fn main() {
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let mut elves = day23::parse_map(&util::parse_input());
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for i in 0..N_ROUNDS {
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let elves_too_close = day23::do_round(&mut elves, i);
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if !elves_too_close {
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break;
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}
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}
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println!("Elves cover {} empty tiles", empty_ground(&elves));
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}
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112
src/day23.rs
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112
src/day23.rs
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use std::collections::{HashMap, HashSet};
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use itertools::Itertools;
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use crate::util::{self, SignedCoord};
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pub fn parse_map(input: &str) -> HashSet<SignedCoord> {
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let mut result = HashSet::new();
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for (y, row) in input.lines().enumerate() {
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for (x, c) in row.chars().enumerate() {
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if c == '#' {
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result.insert((y as isize, x as isize));
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}
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}
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}
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result
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}
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const NUM_DIRS: usize = 4;
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pub fn do_round(elves: &mut HashSet<SignedCoord>, it: usize) -> bool {
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let mut proposals: HashMap<SignedCoord, Vec<SignedCoord>> = HashMap::new();
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let mut elves_too_close = false;
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for elf in elves.iter() {
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if noone_adjacent(elves, elf) {
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continue;
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}
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elves_too_close = true;
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for offset in 0..NUM_DIRS {
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let dir = (it + offset) % NUM_DIRS;
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if let Some(new_loc) = propose(elves, elf, dir) {
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proposals.entry(new_loc).or_insert_with(Vec::new).push(*elf);
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break;
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}
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}
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}
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for (target, interested) in proposals {
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if interested.len() == 1 {
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elves.remove(&interested[0]);
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elves.insert(target);
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}
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}
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elves_too_close
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}
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fn noone_adjacent(elves: &HashSet<SignedCoord>, elf: &SignedCoord) -> bool {
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!(elves.contains(&(elf.0, elf.1 + 1))
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|| elves.contains(&(elf.0, elf.1 - 1))
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|| elves.contains(&(elf.0 + 1, elf.1))
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|| elves.contains(&(elf.0 + 1, elf.1 + 1))
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|| elves.contains(&(elf.0 + 1, elf.1 - 1))
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|| elves.contains(&(elf.0 - 1, elf.1))
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|| elves.contains(&(elf.0 - 1, elf.1 + 1))
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|| elves.contains(&(elf.0 - 1, elf.1 - 1)))
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}
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fn propose(elves: &HashSet<SignedCoord>, elf: &SignedCoord, dir: usize) -> Option<SignedCoord> {
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let (moved, other) = match dir {
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0 => (
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(elf.0 - 1, elf.1),
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((elf.0 - 1, elf.1 - 1), (elf.0 - 1, elf.1 + 1)),
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), // N
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1 => (
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(elf.0 + 1, elf.1),
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((elf.0 + 1, elf.1 - 1), (elf.0 + 1, elf.1 + 1)),
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), // S
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2 => (
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(elf.0, elf.1 - 1),
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((elf.0 - 1, elf.1 - 1), (elf.0 + 1, elf.1 - 1)),
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), // E
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3 => (
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(elf.0, elf.1 + 1),
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((elf.0 - 1, elf.1 + 1), (elf.0 + 1, elf.1 + 1)),
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), // W
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_ => panic!("Unknown direction {}", dir),
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};
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if elves.contains(&moved) || elves.contains(&other.0) || elves.contains(&other.1) {
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None
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} else {
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Some(moved)
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}
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}
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pub fn print_map(elves: &HashSet<SignedCoord>) {
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let (y_min, y_max) = util::minmax_unwrap(&elves.iter().map(|c| c.0).minmax());
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let (x_min, x_max) = util::minmax_unwrap(&elves.iter().map(|c| c.1).minmax());
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println!("({}, {})", y_min, x_min);
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for y in y_min..(y_max + 1) {
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for x in x_min..(x_max + 1) {
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if elves.contains(&(y, x)) {
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print!("#");
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} else {
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print!(".");
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}
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}
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print!("\n");
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}
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print!("\n");
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}
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pub fn empty_ground(elves: &HashSet<SignedCoord>) -> usize {
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let (y_min, y_max) = util::minmax_unwrap(&elves.iter().map(|c| c.0).minmax());
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let (x_min, x_max) = util::minmax_unwrap(&elves.iter().map(|c| c.1).minmax());
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let y_dim = (y_max + 1 - y_min) as usize;
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let x_dim = (x_max + 1 - x_min) as usize;
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y_dim * x_dim - elves.len()
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}
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@ -13,6 +13,7 @@ pub mod day2;
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pub mod day20;
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pub mod day21;
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pub mod day22;
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pub mod day23;
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pub mod day3;
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pub mod day4;
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pub mod day5;
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10
src/util.rs
10
src/util.rs
@ -3,6 +3,8 @@ use std::env;
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use std::fs;
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use std::hash::Hash;
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use itertools::MinMaxResult;
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pub fn parse_input() -> String {
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let args: Vec<String> = env::args().collect();
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let input_path = args
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@ -153,3 +155,11 @@ impl Dir {
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Self::from_usize((d + 3) % 4).unwrap()
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}
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}
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pub fn minmax_unwrap<T: Clone>(mm: &MinMaxResult<T>) -> (T, T) {
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match mm {
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MinMaxResult::NoElements => panic!("No elements"),
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MinMaxResult::OneElement(a) => (a.clone(), a.clone()),
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MinMaxResult::MinMax(a, b) => (a.clone(), b.clone()),
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}
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}
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