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|
use regex::Regex;
use std::collections::HashSet;
fn main() {
let input = advent::read_lines(13);
println!("13a: {}", fold_once(&input));
println!("13b:");
fold_all(&input);
}
#[derive(PartialEq,Eq,Hash,Clone,Copy)]
struct Position {
x: usize,
y: usize,
}
struct Fold {
pos: Position,
}
fn parse_instructions<T: AsRef<str>>(input: &[T]) -> (HashSet<Position>, Vec<Fold>) {
let re_pos = Regex::new(r"^(\d+),(\d+)$").unwrap();
let re_fold = Regex::new(r"^fold along ([xy])=(\d+)$").unwrap();
let mut positions = HashSet::new();
let mut folds = Vec::new();
for line in input {
if let Some(pos) = re_pos.captures(line.as_ref()) {
positions.insert(Position {
x: pos.get(1).unwrap().as_str().parse::<usize>().unwrap(),
y: pos.get(2).unwrap().as_str().parse::<usize>().unwrap(),
});
continue;
}
if let Some(fold) = re_fold.captures(line.as_ref()) {
let axis = fold.get(1).unwrap().as_str();
let coord = fold.get(2).unwrap().as_str().parse::<usize>().unwrap();
match axis {
"x" => folds.push(Fold { pos: Position { x: coord, y: 0 } }),
"y" => folds.push(Fold { pos: Position { x: 0, y: coord } }),
_ => panic!("invalid axis"),
}
}
}
(positions, folds)
}
fn fold(points: &HashSet<Position>, fold: &Fold) -> HashSet<Position> {
let mut new_points = HashSet::new();
for point in points {
if fold.pos.x == 0 {
if point.y < fold.pos.y {
new_points.insert(*point);
} else {
new_points.insert(Position { x: point.x, y: fold.pos.y - (point.y - fold.pos.y) });
}
} else if fold.pos.y == 0 {
if point.x < fold.pos.x {
new_points.insert(*point);
} else {
new_points.insert(Position { x: fold.pos.x - (point.x - fold.pos.x), y: point.y });
}
} else {
panic!("invalid fold");
}
}
new_points
}
fn fold_once<T: AsRef<str>>(input: &[T]) -> usize {
let (positions, folds) = parse_instructions(input);
fold(&positions, &folds[0]).iter().len()
}
fn fold_all<T: AsRef<str>>(input: &[T]) {
let (mut positions, folds) = parse_instructions(input);
for f in folds {
positions = fold(&positions, &f);
}
let max_x = positions.iter().map(|&pos| pos.x).max().unwrap();
let max_y = positions.iter().map(|&pos| pos.y).max().unwrap();
for y in 0 ..= max_y {
for x in 0 ..= max_x {
if positions.contains(&Position { x, y }) {
print!("#");
} else {
print!(".");
}
}
println!();
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"6,10",
"0,14",
"9,10",
"0,3",
"10,4",
"4,11",
"6,0",
"6,12",
"4,1",
"0,13",
"10,12",
"3,4",
"3,0",
"8,4",
"1,10",
"2,14",
"8,10",
"9,0",
"",
"fold along y=7",
"fold along x=5",
];
assert_eq!(fold_once(&input), 17);
}
}
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