Day 12 p1

This commit is contained in:
Tyler Beckman 2024-12-11 23:10:27 -07:00
parent 3ad0212da4
commit 053be764b7
Signed by: Ty
GPG key ID: 2813440C772555A4
2 changed files with 90 additions and 0 deletions

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@ -6,3 +6,7 @@ edition = "2021"
[[bin]] [[bin]]
name = "d11p2" name = "d11p2"
path = "day11/part2.rs" path = "day11/part2.rs"
[[bin]]
name = "d12p1"
path = "day12/part1.rs"

86
day12/part1.rs Normal file
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@ -0,0 +1,86 @@
#![feature(let_chains)]
use std::collections::{HashSet, VecDeque};
const GRID_SIZE: usize = 140;
fn dfs(grid: &[[char; GRID_SIZE]; GRID_SIZE], start: (usize, usize)) -> HashSet<(usize, usize)> {
let mut queue = VecDeque::from([start]);
let mut set = HashSet::from([start]);
let plant_type = grid[start.0][start.1];
while let Some(next) = queue.pop_front() {
let to_check = [
(next.0 + 1, next.1),
(next.0.wrapping_sub(1), next.1),
(next.0, next.1 + 1),
(next.0, next.1.wrapping_sub(1)),
];
for pos in to_check {
if set.contains(&pos) {
continue;
}
if let Some(plant) = grid.get(pos.0).and_then(|r| r.get(pos.1))
&& *plant == plant_type
{
queue.push_back(pos);
set.insert(pos);
}
}
}
set
}
fn main() {
let mut input_iter = include_str!("input.txt").lines().map(|l| {
let mut iter = l.chars();
std::array::from_fn::<_, GRID_SIZE, _>(|_| iter.next().unwrap())
});
let grid: [_; GRID_SIZE] = std::array::from_fn(|_| input_iter.next().unwrap());
// Parse all independent regions
let mut regions = Vec::<HashSet<(usize, usize)>>::new();
for row in 0..GRID_SIZE {
for col in 0..GRID_SIZE {
if regions.iter().all(|region| !region.contains(&(row, col))) {
regions.push(dfs(&grid, (row, col)));
}
}
}
// Sanity check -> are there any duplicated nodes between the regions?
assert_eq!(
regions.iter().map(|r| r.len()).sum::<usize>(),
regions
.iter()
.flatten()
.collect::<HashSet<&(usize, usize)>>()
.len()
);
// Calculate area and perimeter of each
let mut sum = 0;
for region in regions.into_iter() {
let area = region.len();
let mut perimeter_set = Vec::<(Option<usize>, Option<usize>)>::new();
for pos in region.iter() {
let to_check = [
(pos.0.checked_add(1), Some(pos.1)),
(pos.0.checked_sub(1), Some(pos.1)),
(Some(pos.0), pos.1.checked_add(1)),
(Some(pos.0), pos.1.checked_sub(1)),
];
for outer_pos in to_check {
if (outer_pos.0.is_none() || outer_pos.1.is_none())
|| !region.contains(&(outer_pos.0.unwrap(), outer_pos.1.unwrap()))
{
perimeter_set.push(outer_pos);
}
}
}
sum += area * perimeter_set.len();
}
println!("Result: {sum}");
}