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use advent_of_code::prelude::*;
#[derive(Default)]
pub struct Paper {
grid: Grid<bool>,
}
impl Paper {
fn set(&mut self, row: Row, col: Col) {
self.grid.grow(Row(row.0 + 1), Col(col.0 + 1));
self.grid[row][col] = true;
}
fn fold(&mut self, horizontal: bool, coord: usize) {
let mut clone = Self::default();
if horizontal {
clone.grid.grow(
self.grid.rows(),
Col(coord.max(self.grid.cols().0 - coord - 1)),
);
for ((Row(row), Col(col)), cell) in self.grid.indexed_cells() {
if *cell {
if coord > self.grid.cols().0 - coord - 1 {
if col < coord {
clone.set(Row(row), Col(col));
} else if col > coord {
clone.set(Row(row), Col(coord * 2 - col));
}
} else {
if col < coord {
clone.set(
Row(row),
Col(self.grid.cols().0 - coord * 2 - 1 + col),
);
} else if col > coord {
clone.set(
Row(row),
Col(self.grid.cols().0 - col - 1),
);
}
}
}
}
} else {
clone.grid.grow(
Row(coord.max(self.grid.rows().0 - coord - 1)),
self.grid.cols(),
);
for ((Row(row), Col(col)), cell) in self.grid.indexed_cells() {
if *cell {
if coord > self.grid.rows().0 - coord - 1 {
if row < coord {
clone.set(Row(row), Col(col));
} else if row > coord {
clone.set(Row(coord * 2 - row), Col(col));
}
} else {
if row < coord {
clone.set(
Row(self.grid.rows().0 - coord * 2 - 1 + row),
Col(col),
);
} else if row > coord {
clone.set(
Row(self.grid.rows().0 - row - 1),
Col(col),
);
}
}
}
}
}
*self = clone;
}
fn total(&self) -> usize {
self.grid.cells().filter(|b| **b).count()
}
}
impl std::fmt::Display for Paper {
fn fmt(
&self,
f: &mut std::fmt::Formatter<'_>,
) -> Result<(), std::fmt::Error> {
write!(
f,
"{}",
self.grid.display_packed(|b| if *b { '#' } else { '.' })
)
}
}
pub fn parse(fh: File) -> Result<(Paper, Vec<(bool, usize)>)> {
let mut paper = Paper::default();
let mut folds = vec![];
for line in parse::raw_lines(fh) {
if line.is_empty() {
continue;
}
if let Some(fold) = line.strip_prefix("fold along ") {
let mut fold = fold.split('=');
let horizontal = fold.next().unwrap() == "x";
let coord: usize = fold.next().unwrap().parse()?;
folds.push((horizontal, coord));
} else {
let mut coords = line.split(',');
let x: usize = coords.next().unwrap().parse()?;
let y: usize = coords.next().unwrap().parse()?;
paper.set(Row(y), Col(x));
}
}
Ok((paper, folds))
}
pub fn part1(
(mut paper, folds): (Paper, Vec<(bool, usize)>),
) -> Result<usize> {
paper.fold(folds[0].0, folds[0].1);
Ok(paper.total())
}
pub fn part2(
(mut paper, folds): (Paper, Vec<(bool, usize)>),
) -> Result<String> {
for fold in folds {
paper.fold(fold.0, fold.1);
}
Ok(ocr(&paper.to_string()))
}
#[test]
fn test() {
assert_eq!(
part1(parse(parse::data(2021, 13).unwrap()).unwrap()).unwrap(),
678
);
assert_eq!(
part2(parse(parse::data(2021, 13).unwrap()).unwrap()).unwrap(),
"ECFHLHZF"
);
}
|
