day 21
This commit is contained in:
Moritz Hölting
parent
082eb03bc1
commit
0278599411
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@ -1,2 +1,4 @@
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/target
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/erl_crash.dump
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/erl_crash.dump
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zig-out/
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zig-cache/
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@ -206,6 +206,14 @@ dependencies = [
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"num",
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]
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[[package]]
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name = "day-21"
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version = "0.0.0"
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dependencies = [
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"indoc",
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"itertools",
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]
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[[package]]
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name = "deprecate-until"
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version = "0.1.1"
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@ -448,9 +456,9 @@ checksum = "830b246a0e5f20af87141b25c173cd1b609bd7779a4617d6ec582abaf90870f3"
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[[package]]
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name = "pathfinding"
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version = "4.4.0"
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version = "4.6.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "752866d4511516a35883728309499db42696f388263586b70659a5461e641db5"
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checksum = "3ea07a6e677e47d6a84724d4fdf88b1e37fcb49ac94e236d7caeefd8fee75c8a"
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dependencies = [
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"deprecate-until",
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"fixedbitset",
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[package]
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name = "day-21"
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version = "0.0.0"
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edition = "2021"
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[dev-dependencies]
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indoc.workspace = true
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[dependencies]
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itertools.workspace = true
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...................................................................................................................................
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.................................................................S.................................................................
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...................................................................................................................................
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use itertools::Itertools;
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fn main() {
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println!("{}", part1(include_str!("./input.txt"), 64));
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}
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fn part1(input: &str, steps: u32) -> usize {
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let map = input
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.lines()
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.map(|line| line.chars().map(Plot::from).collect())
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.collect::<Vec<Vec<_>>>();
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let starting = map
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.iter()
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.enumerate()
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.find_map(|(y, l)| {
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l.iter().enumerate().find_map(|(x, p)| {
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if p == &Plot::Starting {
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Some((x, 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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.expect("no starting plot");
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let reachable = std::iter::successors(Some(vec![(starting, 0)]), |prev| {
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let next = prev
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.iter()
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.flat_map(|p| {
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successors(*p, &map)
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.into_iter()
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.filter(|(_, cur_steps)| *cur_steps <= steps)
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})
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.sorted()
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.dedup()
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.collect::<Vec<_>>();
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if next.is_empty() {
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None
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} else {
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Some(next)
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}
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})
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.collect::<Vec<_>>();
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reachable.last().expect("no last element").len()
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}
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fn successors(
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((x, y), step_count): ((usize, usize), u32),
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map: &Vec<Vec<Plot>>,
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) -> Vec<((usize, usize), u32)> {
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let mut successors = vec![];
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if x > 0 && map[y][x - 1] != Plot::Stone {
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successors.push(((x - 1, y), step_count + 1));
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}
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if y > 0 && map[y - 1][x] != Plot::Stone {
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successors.push(((x, y - 1), step_count + 1));
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}
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if x < map[0].len() - 1 && map[y][x + 1] != Plot::Stone {
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successors.push(((x + 1, y), step_count + 1));
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}
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if y < map.len() - 1 && map[y + 1][x] != Plot::Stone {
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successors.push(((x, y + 1), step_count + 1));
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}
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successors
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}
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#[derive(Debug, PartialEq, Eq, Clone, Copy)]
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enum Plot {
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Starting,
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Garden,
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Stone,
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}
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impl From<char> for Plot {
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fn from(c: char) -> Self {
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match c {
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'.' => Plot::Garden,
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'#' => Plot::Stone,
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'S' => Plot::Starting,
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_ => panic!("Invalid plot"),
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use indoc::indoc;
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#[test]
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fn test_part1() {
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assert_eq!(
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part1(
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indoc!(
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"
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...........
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.....###.#.
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.###.##..#.
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..#.#...#..
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....#.#....
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.##..S####.
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.##..#...#.
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.......##..
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.##.#.####.
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.##..##.##.
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...........
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"
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),
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6
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),
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16
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);
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}
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}
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@ -0,0 +1,303 @@
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use itertools::Itertools;
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use std::collections::{HashMap, HashSet, VecDeque};
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fn main() {
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println!("{}", part2(include_str!("./input.txt"), 26501365));
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}
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/// Assumptions for part 2:
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/// Line and column of the starting point are completely empty
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/// Borders are completely empty
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/// The garden is of odd size with the starting point in the middle
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/// The garden is a square
|
||||
/// The step count is a whole number of the gardens width plus half the width
|
||||
fn part2(input: &str, steps: u32) -> usize {
|
||||
/* IDEA:
|
||||
the inner repetitions of the garden have all the same amount of reachable plots,
|
||||
grouped by whether they are entered with an odd or even amount of steps.
|
||||
The corners of this diagonal square of reachable plots have the size of the
|
||||
garden minus one steps remaining and are different from each other.
|
||||
the small triangles have half the size of the garden minus one steps remaining
|
||||
and are entered from the corners.
|
||||
the big triangles have the size of the garden plus half the size of the garden
|
||||
of steps remaining and are also entered from the corners.
|
||||
*/
|
||||
|
||||
let map = input
|
||||
.lines()
|
||||
.map(|line| line.chars().map(Plot::from).collect())
|
||||
.collect::<Vec<Vec<_>>>();
|
||||
|
||||
assert!(map.len() == map[0].len(), "garden is not a square");
|
||||
assert!(
|
||||
steps as usize % map.len() == map.len() / 2,
|
||||
"steps is not a whole number of the gardens width plus half the width"
|
||||
);
|
||||
|
||||
let starting = map
|
||||
.iter()
|
||||
.enumerate()
|
||||
.find_map(|(y, l)| {
|
||||
l.iter().enumerate().find_map(|(x, p)| {
|
||||
if p == &Plot::Starting {
|
||||
Some((x, y))
|
||||
} else {
|
||||
None
|
||||
}
|
||||
})
|
||||
})
|
||||
.expect("no starting plot");
|
||||
|
||||
assert!(
|
||||
starting.0 == map.len() / 2 && starting.1 == map.len() / 2,
|
||||
"starting point is not in the middle of the garden"
|
||||
);
|
||||
|
||||
let grid_width = steps as usize / map.len() - 1;
|
||||
|
||||
// round down to even number
|
||||
let odd_grids_amount = (grid_width / 2 * 2 + 1).pow(2);
|
||||
let even_grids_amount = ((grid_width + 1) / 2 * 2).pow(2);
|
||||
|
||||
let odd_points_each = fill(starting, map.len() as u32 * 2 + 1, &map);
|
||||
let even_points_each = fill(starting, map.len() as u32 * 2, &map);
|
||||
|
||||
let top_corner_points = fill((starting.0, map.len() - 1), map.len() as u32 - 1, &map);
|
||||
let right_corner_points = fill((0, starting.1), map.len() as u32 - 1, &map);
|
||||
let bottom_corner_points = fill((starting.0, 0), map.len() as u32 - 1, &map);
|
||||
let left_corner_points = fill((map.len() - 1, starting.1), map.len() as u32 - 1, &map);
|
||||
|
||||
let corner_points =
|
||||
top_corner_points + right_corner_points + bottom_corner_points + left_corner_points;
|
||||
|
||||
let small_top_right_points = fill((0, map.len() - 1), map.len() as u32 / 2 - 1, &map);
|
||||
let small_top_left_points = fill(
|
||||
(map.len() - 1, map.len() - 1),
|
||||
map.len() as u32 / 2 - 1,
|
||||
&map,
|
||||
);
|
||||
let small_bottom_right_points = fill((0, 0), map.len() as u32 / 2 - 1, &map);
|
||||
let small_bottom_left_points = fill((map.len() - 1, 0), map.len() as u32 / 2 - 1, &map);
|
||||
|
||||
let small_points = (small_top_right_points
|
||||
+ small_top_left_points
|
||||
+ small_bottom_right_points
|
||||
+ small_bottom_left_points)
|
||||
* (grid_width + 1);
|
||||
|
||||
let large_top_right_points = fill((0, map.len() - 1), map.len() as u32 * 3 / 2 - 1, &map);
|
||||
let large_top_left_points = fill(
|
||||
(map.len() - 1, map.len() - 1),
|
||||
map.len() as u32 * 3 / 2 - 1,
|
||||
&map,
|
||||
);
|
||||
let large_bottom_right_points = fill((0, 0), map.len() as u32 * 3 / 2 - 1, &map);
|
||||
let large_bottom_left_points = fill((map.len() - 1, 0), map.len() as u32 * 3 / 2 - 1, &map);
|
||||
|
||||
let large_points = (large_top_right_points
|
||||
+ large_top_left_points
|
||||
+ large_bottom_right_points
|
||||
+ large_bottom_left_points)
|
||||
* grid_width;
|
||||
|
||||
odd_grids_amount * odd_points_each
|
||||
+ even_grids_amount * even_points_each
|
||||
+ corner_points
|
||||
+ small_points
|
||||
+ large_points
|
||||
}
|
||||
|
||||
fn fill((starting_x, starting_y): (usize, usize), steps: u32, map: &Vec<Vec<Plot>>) -> usize {
|
||||
let mut ans = HashSet::new();
|
||||
let mut seen = HashSet::new();
|
||||
seen.insert((starting_x, starting_y));
|
||||
let mut queue = VecDeque::new();
|
||||
queue.push_back(((starting_x, starting_y), steps));
|
||||
|
||||
while let Some(((x, y), remaining_steps)) = queue.pop_front() {
|
||||
if remaining_steps % 2 == 0 {
|
||||
ans.insert((x, y));
|
||||
}
|
||||
if remaining_steps == 0 {
|
||||
continue;
|
||||
}
|
||||
|
||||
let directions = [
|
||||
Some((x + 1, y)),
|
||||
x.checked_sub(1).map(|x| (x, y)),
|
||||
Some((x, y + 1)),
|
||||
y.checked_sub(1).map(|y| (x, y)),
|
||||
];
|
||||
|
||||
for (nx, ny) in directions.into_iter().flatten() {
|
||||
if ny >= map.len()
|
||||
|| nx >= map[0].len()
|
||||
|| seen.contains(&(nx, ny))
|
||||
|| map[ny][nx] == Plot::Stone
|
||||
{
|
||||
continue;
|
||||
}
|
||||
seen.insert((nx, ny));
|
||||
queue.push_back(((nx, ny), remaining_steps - 1))
|
||||
}
|
||||
}
|
||||
|
||||
ans.len()
|
||||
}
|
||||
|
||||
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
|
||||
enum Plot {
|
||||
Starting,
|
||||
Garden,
|
||||
Stone,
|
||||
}
|
||||
impl From<char> for Plot {
|
||||
fn from(c: char) -> Self {
|
||||
match c {
|
||||
'.' => Plot::Garden,
|
||||
'#' => Plot::Stone,
|
||||
'S' => Plot::Starting,
|
||||
_ => panic!("Invalid plot"),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
#[allow(dead_code)]
|
||||
/// Bruteforce
|
||||
/// Takes too long
|
||||
fn part2_bruteforce(input: &str, steps: u32) -> usize {
|
||||
let map = input
|
||||
.lines()
|
||||
.map(|line| line.chars().map(Plot::from).collect())
|
||||
.collect::<Vec<Vec<_>>>();
|
||||
|
||||
let starting = map
|
||||
.iter()
|
||||
.enumerate()
|
||||
.find_map(|(y, l)| {
|
||||
l.iter().enumerate().find_map(|(x, p)| {
|
||||
if p == &Plot::Starting {
|
||||
Some((x as i128, y as i128))
|
||||
} else {
|
||||
None
|
||||
}
|
||||
})
|
||||
})
|
||||
.expect("no starting plot");
|
||||
|
||||
let mut visited = HashSet::new();
|
||||
visited.insert(starting);
|
||||
let mut new = HashSet::new();
|
||||
new.insert(starting);
|
||||
let mut cache = HashMap::new();
|
||||
cache.insert(0, 1);
|
||||
|
||||
let reachable = std::iter::successors(Some(vec![(starting, 0)]), |prev| {
|
||||
let next = prev
|
||||
.iter()
|
||||
.flat_map(|p| {
|
||||
successors(*p, &map)
|
||||
.into_iter()
|
||||
.filter(|(_, cur_steps)| *cur_steps <= steps)
|
||||
})
|
||||
.sorted()
|
||||
.dedup()
|
||||
.collect::<Vec<_>>();
|
||||
if next.is_empty() {
|
||||
None
|
||||
} else {
|
||||
Some(next)
|
||||
}
|
||||
})
|
||||
.collect::<Vec<_>>();
|
||||
|
||||
reachable.last().expect("no last element").len()
|
||||
}
|
||||
|
||||
fn successors(
|
||||
((x, y), step_count): ((i128, i128), u32),
|
||||
map: &Vec<Vec<Plot>>,
|
||||
) -> Vec<((i128, i128), u32)> {
|
||||
let height = map.len();
|
||||
let width = map[0].len();
|
||||
let ux = (x.rem_euclid(width as i128)) as usize;
|
||||
let uy = (y.rem_euclid(height as i128)) as usize;
|
||||
let mut successors = vec![];
|
||||
if (ux > 0 && map[uy][ux - 1] != Plot::Stone) || (ux == 0 && map[uy][width - 1] != Plot::Stone)
|
||||
{
|
||||
successors.push(((x - 1, y), step_count + 1));
|
||||
}
|
||||
if (uy > 0 && map[uy - 1][ux] != Plot::Stone) || (uy == 0 && map[height - 1][ux] != Plot::Stone)
|
||||
{
|
||||
successors.push(((x, y - 1), step_count + 1));
|
||||
}
|
||||
if (ux < width - 1 && map[uy][ux + 1] != Plot::Stone)
|
||||
|| (ux == width - 1 && map[uy][0] != Plot::Stone)
|
||||
{
|
||||
successors.push(((x + 1, y), step_count + 1));
|
||||
}
|
||||
if (uy < height - 1 && map[uy + 1][ux] != Plot::Stone)
|
||||
|| (uy == height - 1 && map[0][ux] != Plot::Stone)
|
||||
{
|
||||
successors.push(((x, y + 1), step_count + 1));
|
||||
}
|
||||
successors
|
||||
}
|
||||
|
||||
#[cfg(test)]
|
||||
mod tests {
|
||||
use super::*;
|
||||
use indoc::indoc;
|
||||
|
||||
const INPUT: &str = indoc!(
|
||||
"
|
||||
...........
|
||||
.....###.#.
|
||||
.###.##..#.
|
||||
..#.#...#..
|
||||
....#.#....
|
||||
.##..S####.
|
||||
.##..#...#.
|
||||
.......##..
|
||||
.##.#.####.
|
||||
.##..##.##.
|
||||
...........
|
||||
"
|
||||
);
|
||||
|
||||
#[test]
|
||||
#[ignore = "not working because of assumptions"]
|
||||
fn test_part2_6() {
|
||||
assert_eq!(part2(INPUT, 6), 16);
|
||||
}
|
||||
#[test]
|
||||
#[ignore = "not working because of assumptions"]
|
||||
fn test_part2_10() {
|
||||
assert_eq!(part2(INPUT, 10), 50);
|
||||
}
|
||||
#[test]
|
||||
#[ignore = "not working because of assumptions"]
|
||||
fn test_part2_50() {
|
||||
assert_eq!(part2(INPUT, 50), 1594);
|
||||
}
|
||||
#[test]
|
||||
#[ignore = "not working because of assumptions"]
|
||||
fn test_part2_100() {
|
||||
assert_eq!(part2(INPUT, 100), 6536);
|
||||
}
|
||||
#[test]
|
||||
#[ignore = "not working because of assumptions"]
|
||||
fn test_part2_500() {
|
||||
assert_eq!(part2(INPUT, 500), 167004);
|
||||
}
|
||||
#[test]
|
||||
#[ignore = "not working because of assumptions"]
|
||||
fn test_part2_1000() {
|
||||
assert_eq!(part2(INPUT, 1000), 668697);
|
||||
}
|
||||
#[test]
|
||||
#[ignore = "not working because of assumptions"]
|
||||
fn test_part2_5000() {
|
||||
assert_eq!(part2(INPUT, 5000), 16733044);
|
||||
}
|
||||
}
|
||||
Loading…
Reference in New Issue