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22.rs
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22.rs
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static INPUT_TXT: &str = include_str!("../../input/22.txt");
const GRID_SIZE: usize = 50;
fn main() {
println!("Part 1: {}", part_1(INPUT_TXT));
println!("Part 2: {}", part_2(INPUT_TXT));
}
#[derive(Debug, Clone)]
struct Position {
x: usize,
y: usize,
facing: i64,
}
impl Position {
fn left(&mut self) {
self.facing += if self.facing == 0 { 3 } else { -1 };
}
fn right(&mut self) {
self.facing = (self.facing + 1).rem_euclid(4);
}
fn next_position(&self, map: &[Vec<char>]) -> Self {
let (x, y) = match self.facing {
0 => (
if map[self.y].len() - 1 > self.x {
self.x + 1
} else {
map[self.y].iter().position(|c| *c != ' ').unwrap()
},
self.y,
),
1 => (
self.x,
if map.len() - 1 > self.y
&& map[self.y + 1].len() > self.x
&& map[self.y + 1][self.x] != ' '
{
self.y + 1
} else {
map.iter()
.position(|l| l.len() > self.x && l[self.x] != ' ')
.unwrap()
},
),
2 => (
if self.x == 0 || map[self.y][self.x - 1] == ' ' {
map[self.y].len() - 1
} else {
self.x - 1
},
self.y,
),
3 => (
self.x,
if self.y == 0 || map[self.y - 1][self.x] == ' ' {
map.iter()
.rposition(|l| l.len() > self.x && l[self.x] != ' ')
.unwrap()
} else {
self.y - 1
},
),
_ => unreachable!(),
};
Self {
x,
y,
facing: self.facing,
}
}
fn cube_next_position(&self, map: &[Vec<char>]) -> Self {
match self.facing {
0 => {
if map[self.y].len() - 1 > self.x {
Self {
x: self.x + 1,
y: self.y,
facing: self.facing,
}
} else if self.y < GRID_SIZE {
Self {
x: 2 * GRID_SIZE - 1,
y: 3 * GRID_SIZE - 1 - self.y,
facing: 2,
}
} else if self.y < 2 * GRID_SIZE {
Self {
x: GRID_SIZE + self.y,
y: GRID_SIZE - 1,
facing: 3,
}
} else if self.y < 3 * GRID_SIZE {
Self {
x: 3 * GRID_SIZE - 1,
y: 3 * GRID_SIZE - self.y - 1,
facing: 2,
}
} else {
Self {
x: self.y - 2 * GRID_SIZE,
y: 3 * GRID_SIZE - 1,
facing: 3,
}
}
}
1 => {
if map.len() - 1 > self.y
&& map[self.y + 1].len() > self.x
&& map[self.y + 1][self.x] != ' '
{
Self {
x: self.x,
y: self.y + 1,
facing: self.facing,
}
} else if self.x < GRID_SIZE {
Self {
x: self.x + 2 * GRID_SIZE,
y: 0,
facing: self.facing,
}
} else if self.x < 2 * GRID_SIZE {
Self {
x: GRID_SIZE - 1,
y: self.x + 2 * GRID_SIZE,
facing: 2,
}
} else {
Self {
x: 2 * GRID_SIZE - 1,
y: self.x - GRID_SIZE,
facing: 2,
}
}
}
2 => {
if self.x != 0 && map[self.y][self.x - 1] != ' ' {
Self {
x: self.x - 1,
y: self.y,
facing: self.facing,
}
} else if self.y < GRID_SIZE {
Self {
x: 0,
y: 3 * GRID_SIZE - 1 - self.y,
facing: 0,
}
} else if self.y < 2 * GRID_SIZE {
Self {
x: self.y - GRID_SIZE,
y: 2 * GRID_SIZE,
facing: 1,
}
} else if self.y < 3 * GRID_SIZE {
Self {
x: GRID_SIZE,
y: 3 * GRID_SIZE - 1 - self.y,
facing: 0,
}
} else {
Self {
x: self.y - 2 * GRID_SIZE,
y: 0,
facing: 1,
}
}
}
3 => {
if self.y != 0 && map[self.y - 1][self.x] != ' ' {
Self {
x: self.x,
y: self.y - 1,
facing: self.facing,
}
} else if self.x < GRID_SIZE {
Self {
x: GRID_SIZE,
y: self.x + GRID_SIZE,
facing: 0,
}
} else if self.x < 2 * GRID_SIZE {
Self {
x: 0,
y: self.x + 2 * GRID_SIZE,
facing: 0,
}
} else {
Self {
x: self.x - 2 * GRID_SIZE,
y: 4 * GRID_SIZE - 1,
facing: self.facing,
}
}
}
_ => unreachable!(),
}
}
}
fn walk(map: &[Vec<char>], mut path: &str, cube: bool) -> i64 {
let x = map[0].iter().position(|c| *c == '.').unwrap();
let mut pos = Position { x, y: 0, facing: 0 };
loop {
if path.is_empty() {
break 1000 * (pos.y + 1) as i64 + 4 * (pos.x + 1) as i64 + pos.facing;
}
match &path[..1] {
"L" => {
pos.left();
path = &path[1..];
}
"R" => {
pos.right();
path = &path[1..];
}
_ => {
let len = path.find(|c: char| !c.is_numeric()).unwrap_or(path.len());
let steps = path[..len].parse::<usize>().unwrap();
path = &path[len..];
pos = (0..steps).fold(pos, |pos, _| {
let next = if cube {
pos.cube_next_position(map)
} else {
pos.next_position(map)
};
if map[next.y][next.x] != '#' {
next
} else {
pos
}
});
}
}
}
}
fn part_1(input: &str) -> i64 {
let (map, directions) = input.split_once("\n\n").unwrap();
walk(
&map.lines()
.map(|l| l.chars().collect::<Vec<char>>())
.collect::<Vec<_>>(),
directions.trim(),
false,
)
}
fn part_2(input: &str) -> i64 {
let (map, directions) = input.split_once("\n\n").unwrap();
walk(
&map.lines()
.map(|l| l.chars().collect::<Vec<char>>())
.collect::<Vec<_>>(),
directions.trim(),
true,
)
}
#[cfg(test)]
mod day_22_tests {
use super::*;
static INPUT: &str = " ...#
.#..
#...
....
...#.......#
........#...
..#....#....
..........#.
...#....
.....#..
.#......
......#.
10R5L5R10L4R5L5";
#[test]
fn test_part_1() {
assert_eq!(part_1(INPUT), 6032);
assert_eq!(part_1(INPUT_TXT), 60362);
}
#[test]
fn test_part_2() {
//assert_eq!(part_2(INPUT), 5031);
assert_eq!(part_2(INPUT_TXT), 74288);
}
}