Day 23, part 1

This commit is contained in:
jazzpi 2022-12-23 12:28:17 +01:00
parent 62c866abf9
commit 7abd632567
4 changed files with 142 additions and 0 deletions

19
src/bin/d23p1.rs Normal file
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@ -0,0 +1,19 @@
use aoc22::{
day23::{self, empty_ground},
util,
};
const N_ROUNDS: usize = 10;
pub fn main() {
let mut elves = day23::parse_map(&util::parse_input());
for i in 0..N_ROUNDS {
let elves_too_close = day23::do_round(&mut elves, i);
if !elves_too_close {
break;
}
}
println!("Elves cover {} empty tiles", empty_ground(&elves));
}

112
src/day23.rs Normal file
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@ -0,0 +1,112 @@
use std::collections::{HashMap, HashSet};
use itertools::Itertools;
use crate::util::{self, SignedCoord};
pub fn parse_map(input: &str) -> HashSet<SignedCoord> {
let mut result = HashSet::new();
for (y, row) in input.lines().enumerate() {
for (x, c) in row.chars().enumerate() {
if c == '#' {
result.insert((y as isize, x as isize));
}
}
}
result
}
const NUM_DIRS: usize = 4;
pub fn do_round(elves: &mut HashSet<SignedCoord>, it: usize) -> bool {
let mut proposals: HashMap<SignedCoord, Vec<SignedCoord>> = HashMap::new();
let mut elves_too_close = false;
for elf in elves.iter() {
if noone_adjacent(elves, elf) {
continue;
}
elves_too_close = true;
for offset in 0..NUM_DIRS {
let dir = (it + offset) % NUM_DIRS;
if let Some(new_loc) = propose(elves, elf, dir) {
proposals.entry(new_loc).or_insert_with(Vec::new).push(*elf);
break;
}
}
}
for (target, interested) in proposals {
if interested.len() == 1 {
elves.remove(&interested[0]);
elves.insert(target);
}
}
elves_too_close
}
fn noone_adjacent(elves: &HashSet<SignedCoord>, elf: &SignedCoord) -> bool {
!(elves.contains(&(elf.0, elf.1 + 1))
|| elves.contains(&(elf.0, elf.1 - 1))
|| elves.contains(&(elf.0 + 1, elf.1))
|| elves.contains(&(elf.0 + 1, elf.1 + 1))
|| elves.contains(&(elf.0 + 1, elf.1 - 1))
|| elves.contains(&(elf.0 - 1, elf.1))
|| elves.contains(&(elf.0 - 1, elf.1 + 1))
|| elves.contains(&(elf.0 - 1, elf.1 - 1)))
}
fn propose(elves: &HashSet<SignedCoord>, elf: &SignedCoord, dir: usize) -> Option<SignedCoord> {
let (moved, other) = match dir {
0 => (
(elf.0 - 1, elf.1),
((elf.0 - 1, elf.1 - 1), (elf.0 - 1, elf.1 + 1)),
), // N
1 => (
(elf.0 + 1, elf.1),
((elf.0 + 1, elf.1 - 1), (elf.0 + 1, elf.1 + 1)),
), // S
2 => (
(elf.0, elf.1 - 1),
((elf.0 - 1, elf.1 - 1), (elf.0 + 1, elf.1 - 1)),
), // E
3 => (
(elf.0, elf.1 + 1),
((elf.0 - 1, elf.1 + 1), (elf.0 + 1, elf.1 + 1)),
), // W
_ => panic!("Unknown direction {}", dir),
};
if elves.contains(&moved) || elves.contains(&other.0) || elves.contains(&other.1) {
None
} else {
Some(moved)
}
}
pub fn print_map(elves: &HashSet<SignedCoord>) {
let (y_min, y_max) = util::minmax_unwrap(&elves.iter().map(|c| c.0).minmax());
let (x_min, x_max) = util::minmax_unwrap(&elves.iter().map(|c| c.1).minmax());
println!("({}, {})", y_min, x_min);
for y in y_min..(y_max + 1) {
for x in x_min..(x_max + 1) {
if elves.contains(&(y, x)) {
print!("#");
} else {
print!(".");
}
}
print!("\n");
}
print!("\n");
}
pub fn empty_ground(elves: &HashSet<SignedCoord>) -> usize {
let (y_min, y_max) = util::minmax_unwrap(&elves.iter().map(|c| c.0).minmax());
let (x_min, x_max) = util::minmax_unwrap(&elves.iter().map(|c| c.1).minmax());
let y_dim = (y_max + 1 - y_min) as usize;
let x_dim = (x_max + 1 - x_min) as usize;
y_dim * x_dim - elves.len()
}

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@ -13,6 +13,7 @@ pub mod day2;
pub mod day20;
pub mod day21;
pub mod day22;
pub mod day23;
pub mod day3;
pub mod day4;
pub mod day5;

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@ -3,6 +3,8 @@ use std::env;
use std::fs;
use std::hash::Hash;
use itertools::MinMaxResult;
pub fn parse_input() -> String {
let args: Vec<String> = env::args().collect();
let input_path = args
@ -153,3 +155,11 @@ impl Dir {
Self::from_usize((d + 3) % 4).unwrap()
}
}
pub fn minmax_unwrap<T: Clone>(mm: &MinMaxResult<T>) -> (T, T) {
match mm {
MinMaxResult::NoElements => panic!("No elements"),
MinMaxResult::OneElement(a) => (a.clone(), a.clone()),
MinMaxResult::MinMax(a, b) => (a.clone(), b.clone()),
}
}