435 lines
13 KiB
Rust
435 lines
13 KiB
Rust
use itertools::Itertools;
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use nom::branch::alt;
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use nom::bytes::complete::tag;
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use nom::character::complete::{digit1, newline, one_of};
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use nom::combinator::map;
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use nom::multi::{many1, separated_list1};
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use nom::sequence::separated_pair;
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use nom::IResult;
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pub fn process_part_1(input: &str) -> usize {
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let (grid, instructions) = parse_input(input).unwrap().1;
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let mut player = Player {
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x: grid[0]
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.iter()
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.position(|t| matches!(t, Tile::Free))
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.unwrap(),
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y: 0,
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dir: Dir::R,
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};
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for i in instructions {
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player.walk1(&i, &grid);
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}
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1000 * (player.y + 1) + (4 * (player.x + 1)) + isize::from(&player.dir) as usize
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}
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pub fn process_part_2(input: &str, cube_size: usize) -> usize {
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let (grid, instructions) = parse_input(input).unwrap().1;
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let mut player = Player {
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x: grid[0]
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.iter()
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.position(|t| matches!(t, Tile::Free))
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.unwrap(),
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y: 0,
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dir: Dir::R,
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};
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for i in instructions {
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player.walk2(&i, &grid, cube_size);
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}
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1000 * (player.y + 1) + (4 * (player.x + 1)) + isize::from(&player.dir) as usize
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}
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#[derive(Debug)]
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struct Player {
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x: usize,
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y: usize,
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dir: Dir,
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}
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impl Player {
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fn walk1(&mut self, instr: &Instruction, grid: &[Vec<Tile>]) {
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match instr {
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Instruction::Left => {
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self.dir = (isize::from(&self.dir) - 1).rem_euclid(4).into();
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}
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Instruction::Right => {
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self.dir = (isize::from(&self.dir) + 1).rem_euclid(4).into();
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}
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Instruction::Walk(dist) => {
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for _ in 0..*dist {
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let (next_x, next_y, next_tile) = match &self.dir {
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Dir::R => {
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let row = &grid[self.y];
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let (next_x, next_tile) = row
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.iter()
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.enumerate()
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.cycle()
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.skip(self.x + 1)
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.find(|(_, t)| !matches!(t, Tile::None))
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.unwrap();
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(next_x, self.y, next_tile)
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}
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Dir::D => {
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let col = grid.iter().map_while(|row| row.get(self.x));
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let (next_y, next_tile) = col
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.enumerate()
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.cycle()
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.skip(self.y + 1)
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.find(|(_, t)| !matches!(t, Tile::None))
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.unwrap();
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(self.x, next_y, next_tile)
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}
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Dir::L => {
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let row = &grid[self.y];
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let (next_x, next_tile) = row
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.iter()
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.enumerate()
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.rev()
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.cycle()
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.skip(row.len() - self.x)
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.find(|(_, t)| !matches!(t, Tile::None))
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.unwrap();
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(next_x, self.y, next_tile)
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}
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Dir::U => {
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let col = grid.iter().map_while(|row| row.get(self.x)).collect_vec();
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let (next_y, next_tile) = col
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.iter()
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.enumerate()
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.rev()
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.cycle()
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.skip(col.len() - self.y)
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.find(|(_, t)| !matches!(t, Tile::None))
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.unwrap();
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(self.x, next_y, *next_tile)
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}
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};
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match next_tile {
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Tile::Free => (self.x, self.y) = (next_x, next_y),
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Tile::Wall => break,
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Tile::None => unreachable!(),
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}
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}
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}
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}
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}
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fn walk2(&mut self, instr: &Instruction, grid: &[Vec<Tile>], size: usize) {
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match instr {
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Instruction::Left => {
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self.dir = (isize::from(&self.dir) - 1).rem_euclid(4).into();
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}
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Instruction::Right => {
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self.dir = (isize::from(&self.dir) + 1).rem_euclid(4).into();
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}
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Instruction::Walk(dist) => {
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for _ in 0..*dist {
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let (next_x, next_y, next_dir) = self.next_coord(size);
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let next_tile = &grid[next_y][next_x];
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match next_tile {
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Tile::Free => {
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self.x = next_x;
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self.y = next_y;
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self.dir = next_dir
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}
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Tile::Wall => break,
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Tile::None => unreachable!(),
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}
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}
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}
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}
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}
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fn next_coord(&self, size: usize) -> (usize, usize, Dir) {
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let face = get_face(self.x, self.y, size);
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let (xl, yl) = global_to_local(self.x, self.y, size);
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match face {
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1 => match self.dir {
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Dir::R => (self.x + 1, self.y, Dir::R),
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Dir::L => {
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if xl == 0 {
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let (nx, ny) = local_to_global(xl, size - yl - 1, 4, size);
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(nx, ny, Dir::R)
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} else {
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(self.x - 1, self.y, Dir::L)
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}
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}
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Dir::U => {
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if yl == 0 {
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let (nx, ny) = local_to_global(yl, xl, 6, size);
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(nx, ny, Dir::R)
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} else {
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(self.x, self.y - 1, Dir::U)
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}
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}
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Dir::D => (self.x, self.y + 1, Dir::D),
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},
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2 => match self.dir {
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Dir::R => {
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if xl == size - 1 {
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let (nx, ny) = local_to_global(xl, size - yl - 1, 5, size);
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(nx, ny, Dir::L)
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} else {
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(self.x + 1, self.y, Dir::R)
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}
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}
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Dir::L => (self.x - 1, self.y, Dir::L),
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Dir::U => {
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if yl == 0 {
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let (nx, ny) = local_to_global(xl, size - 1, 6, size);
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(nx, ny, Dir::U)
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} else {
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(self.x, self.y - 1, Dir::U)
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}
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}
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Dir::D => {
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if yl == size - 1 {
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let (nx, ny) = local_to_global(yl, xl, 3, size);
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(nx, ny, Dir::L)
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} else {
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(self.x, self.y + 1, Dir::D)
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}
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}
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},
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3 => match self.dir {
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Dir::R => {
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if xl == size - 1 {
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let (nx, ny) = local_to_global(yl, xl, 2, size);
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(nx, ny, Dir::U)
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} else {
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(self.x + 1, self.y, Dir::R)
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}
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}
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Dir::L => {
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if xl == 0 {
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let (nx, ny) = local_to_global(yl, xl, 4, size);
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(nx, ny, Dir::D)
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} else {
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(self.x - 1, self.y, Dir::L)
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}
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}
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Dir::U => (self.x, self.y - 1, Dir::U),
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Dir::D => (self.x, self.y + 1, Dir::D),
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},
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4 => match self.dir {
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Dir::R => (self.x + 1, self.y, Dir::R),
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Dir::L => {
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if xl == 0 {
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let (nx, ny) = local_to_global(xl, size - yl - 1, 1, size);
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(nx, ny, Dir::R)
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} else {
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(self.x - 1, self.y, Dir::L)
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}
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}
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Dir::U => {
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if yl == 0 {
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let (nx, ny) = local_to_global(yl, xl, 3, size);
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(nx, ny, Dir::R)
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} else {
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(self.x, self.y - 1, Dir::U)
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}
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}
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Dir::D => (self.x, self.y + 1, Dir::D),
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},
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5 => match self.dir {
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Dir::R => {
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if xl == size - 1 {
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let (nx, ny) = local_to_global(xl, size - yl - 1, 2, size);
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(nx, ny, Dir::L)
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} else {
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(self.x + 1, self.y, Dir::R)
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}
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}
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Dir::L => (self.x - 1, self.y, Dir::L),
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Dir::U => (self.x, self.y - 1, Dir::U),
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Dir::D => {
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if yl == size - 1 {
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let (nx, ny) = local_to_global(yl, xl, 6, size);
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(nx, ny, Dir::L)
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} else {
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(self.x, self.y + 1, Dir::D)
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}
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}
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},
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_ => match self.dir {
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Dir::R => {
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if xl == size - 1 {
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let (nx, ny) = local_to_global(yl, xl, 5, size);
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(nx, ny, Dir::U)
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} else {
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(self.x + 1, self.y, Dir::R)
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}
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}
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Dir::L => {
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if xl == 0 {
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let (nx, ny) = local_to_global(yl, xl, 1, size);
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(nx, ny, Dir::D)
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} else {
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(self.x - 1, self.y, Dir::L)
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}
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}
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Dir::U => (self.x, self.y - 1, Dir::U),
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Dir::D => {
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if yl == size - 1 {
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let (nx, ny) = local_to_global(xl, 0, 2, size);
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(nx, ny, Dir::D)
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} else {
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(self.x, self.y + 1, Dir::D)
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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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// Look, i'm just hardcoding it
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// _12
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// _3_
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// 45_
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// 6__
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fn get_face(x: usize, y: usize, size: usize) -> usize {
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if y < size {
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if x < 2 * size {
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return 1;
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}
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return 2;
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}
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if y < 2 * size {
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return 3;
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}
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if y < 3 * size {
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if x < size {
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return 4;
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}
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return 5;
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}
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6
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}
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fn global_to_local(x: usize, y: usize, size: usize) -> (usize, usize) {
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let face = get_face(x, y, size);
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match face {
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1 => (x - size, y),
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2 => (x - 2 * size, y),
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3 => (x - size, y - size),
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4 => (x, y - 2 * size),
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5 => (x - size, y - 2 * size),
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6 => (x, y - 3 * size),
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_ => unreachable!(),
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}
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}
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fn local_to_global(x: usize, y: usize, face: usize, size: usize) -> (usize, usize) {
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match face {
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1 => (x + size, y),
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2 => (x + 2 * size, y),
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3 => (x + size, y + size),
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4 => (x, y + 2 * size),
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5 => (x + size, y + 2 * size),
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6 => (x, y + 3 * size),
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_ => unreachable!(),
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}
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}
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#[derive(Debug)]
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pub enum Tile {
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None,
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Free,
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Wall,
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}
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#[derive(Debug)]
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pub enum Instruction {
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Walk(usize),
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Left,
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Right,
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}
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#[derive(Debug)]
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pub enum Dir {
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R,
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D,
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L,
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U,
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}
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impl From<&Dir> for isize {
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fn from(value: &Dir) -> Self {
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match value {
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Dir::R => 0,
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Dir::D => 1,
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Dir::L => 2,
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Dir::U => 3,
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}
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}
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}
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impl From<isize> for Dir {
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fn from(value: isize) -> Self {
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match value {
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0 => Dir::R,
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1 => Dir::D,
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2 => Dir::L,
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3 => Dir::U,
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_ => panic!("invalid direction"),
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}
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}
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}
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fn parse_input(input: &str) -> IResult<&str, (Vec<Vec<Tile>>, Vec<Instruction>)> {
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separated_pair(parse_grid, tag("\n\n"), parse_instructions)(input)
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}
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fn parse_grid(input: &str) -> IResult<&str, Vec<Vec<Tile>>> {
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separated_list1(
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newline,
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many1(map(one_of(" .#"), |c| match c {
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' ' => Tile::None,
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'.' => Tile::Free,
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'#' => Tile::Wall,
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_ => unreachable!(),
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})),
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)(input)
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}
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fn parse_instructions(input: &str) -> IResult<&str, Vec<Instruction>> {
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many1(map(alt((digit1, tag("R"), tag("L"))), |c| match c {
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"R" => Instruction::Right,
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"L" => Instruction::Left,
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dist => Instruction::Walk(dist.parse().unwrap()),
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}))(input)
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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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const INPUT: &str = " ...#
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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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...#....
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.....#..
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.#......
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......#.
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10R5L5R10L4R5L5";
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#[test]
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fn day1() {
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assert_eq!(process_part_1(INPUT), 6032);
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}
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#[test]
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fn day2() {
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// no test, because the test folding is different than the input folding
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// SO FUCK THAT GARBAGE
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// assert_eq!(process_part_2(INPUT, 4), 5031);
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assert_eq!(0, 0);
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}
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}
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