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#![allow(dead_code)]
#![allow(unused_variables)]
use advent_of_code::prelude::*;
#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
enum Direction {
Up,
Down,
Left,
Right,
}
impl Direction {
fn from_pos(row: Row, col: Col, new_row: Row, new_col: Col) -> Self {
if row.abs_diff(new_row) == Row(1) && col.abs_diff(new_col) == Col(0)
{
if row > new_row {
Self::Up
} else {
Self::Down
}
} else if col.abs_diff(new_col) == Col(1)
&& row.abs_diff(new_row) == Row(0)
{
if col > new_col {
Self::Left
} else {
Self::Right
}
} else {
panic!("invalid direction ({row:?}, {col:?}) -> ({new_row:?}, {new_col:?})")
}
}
fn horizontal(&self) -> bool {
matches!(self, Self::Left | Self::Right)
}
fn increasing(&self) -> bool {
matches!(self, Self::Down | Self::Right)
}
fn turns(&self) -> [Self; 2] {
match self {
Self::Up | Self::Down => [Self::Left, Self::Right],
Self::Left | Self::Right => [Self::Up, Self::Down],
}
}
fn turn_left(&self) -> Self {
match self {
Direction::Up => Direction::Left,
Direction::Down => Direction::Right,
Direction::Left => Direction::Down,
Direction::Right => Direction::Up,
}
}
fn turn_right(&self) -> Self {
match self {
Direction::Up => Direction::Right,
Direction::Down => Direction::Left,
Direction::Left => Direction::Up,
Direction::Right => Direction::Down,
}
}
fn offset(&self) -> (IRow, ICol) {
match self {
Self::Up => (IRow(-1), ICol(0)),
Self::Down => (IRow(1), ICol(0)),
Self::Left => (IRow(0), ICol(-1)),
Self::Right => (IRow(0), ICol(1)),
}
}
}
#[derive(Debug)]
pub struct Instruction {
direction: Direction,
distance: isize,
real_direction: Direction,
real_distance: isize,
}
impl std::str::FromStr for Instruction {
type Err = anyhow::Error;
fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
let cap = regex_captures!(
r"^(U|D|L|R) (\d+) \(#([0-9a-f]{5})([0-9a-f])\)",
s
)
.ok_or_else(|| anyhow::anyhow!("failed to parse line"))?;
let direction = match &cap[1] {
"U" => Direction::Up,
"D" => Direction::Down,
"L" => Direction::Left,
"R" => Direction::Right,
_ => bail!("unknown direction {}", &cap[1]),
};
let distance = cap[2].parse()?;
let real_direction = match &cap[4] {
"0" => Direction::Right,
"1" => Direction::Down,
"2" => Direction::Left,
"3" => Direction::Up,
_ => bail!("unknown real direction in {}", &cap[4]),
};
let real_distance = isize::from_str_radix(&cap[3], 16)?;
Ok(Self {
direction,
distance,
real_direction,
real_distance,
})
}
}
pub fn parse(fh: File) -> Result<Vec<Instruction>> {
Ok(parse::lines(fh).collect())
}
pub fn part1(instructions: Vec<Instruction>) -> Result<i64> {
let mut map: Grid<bool> = Grid::default();
let mut pos = (IRow(0), ICol(0));
let mut corners = vec![pos];
for instruction in &instructions {
let offset = instruction.direction.offset();
pos = (
pos.0 + offset.0 * instruction.distance,
pos.1 + offset.1 * instruction.distance,
);
corners.push(pos);
}
let min_row = corners.iter().map(|(row, _)| row).min().unwrap();
let min_col = corners.iter().map(|(_, col)| col).min().unwrap();
let starting_pos =
(Row(min_row.0.abs_diff(0)), Col(min_col.0.abs_diff(0)));
let mut pos = starting_pos;
for instruction in &instructions {
let offset = instruction.direction.offset();
for _ in 0..instruction.distance {
pos = (
Row(pos.0 .0.checked_add_signed(offset.0 .0).unwrap()),
Col(pos.1 .0.checked_add_signed(offset.1 .0).unwrap()),
);
map.grow(pos.0 + 1, pos.1 + 1);
map[pos.0][pos.1] = true;
}
}
let trench: HashSet<_> = map
.indexed_cells()
.filter_map(
|((row, col), dug)| if *dug { Some((row, col)) } else { None },
)
.collect();
let mut internal_cell = None;
for (row, col) in map.adjacent(starting_pos.0, starting_pos.1, true) {
if trench.contains(&(row, col)) {
continue;
}
let mut count = 0;
for offset in 0..=(row.0.min(col.0)) {
let check_row = row - offset;
let check_col = col - offset;
if trench.contains(&(check_row, check_col)) {
count += 1;
}
}
if count % 2 == 1 {
internal_cell = Some((row, col));
}
}
let internal_cell = internal_cell.unwrap();
map.flood_fill(internal_cell.0, internal_cell.1, &true, true);
Ok(map.cells().filter(|dug| **dug).count().try_into().unwrap())
}
pub fn part2(instructions: Vec<Instruction>) -> Result<i64> {
let mut pos = (IRow(0), ICol(0));
let mut vertices = vec![pos];
let mut last_left = false;
for pair in instructions.windows(2) {
let instruction = &pair[0];
let next_instruction = &pair[1];
let mut distance = instruction.real_distance + 1;
if last_left {
distance -= 1;
}
if instruction.real_direction.turn_left()
== next_instruction.real_direction
{
distance -= 1;
last_left = true;
} else {
last_left = false;
}
let offset = instruction.real_direction.offset();
pos = (pos.0 + offset.0 * distance, pos.1 + offset.1 * distance);
vertices.push(pos);
}
let mut area = 0;
for i in 0..vertices.len() {
let next = if i == vertices.len() - 1 { 0 } else { i + 1 };
area += vertices[i].0 .0 * vertices[next].1 .0
- vertices[next].0 .0 * vertices[i].1 .0;
}
area /= 2;
Ok(area.abs().try_into().unwrap())
}
#[test]
fn test() {
assert_eq!(
part1(parse(parse::data(2023, 18).unwrap()).unwrap()).unwrap(),
36807
);
assert_eq!(
part2(parse(parse::data(2023, 18).unwrap()).unwrap()).unwrap(),
48797603984357
);
}
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