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use nom::{
branch::alt,
bytes::complete::tag,
character::complete::{char as nom_char, line_ending, u32 as nom_u32},
combinator::map,
multi::{many0, separated_list1},
sequence::tuple,
IResult,
};
use std::{collections::BTreeSet, fmt, fs};
fn main() -> Result<(), Box<dyn std::error::Error>> {
let input = fs::read_to_string("inputs/day_13.txt")?;
let mut page = parse_page(&input).unwrap().1;
page.do_next_fold();
dbg!(page.count_points());
while page.do_next_fold() {}
println!("{}", page);
Ok(())
}
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
struct Point {
x: u32,
y: u32,
}
#[derive(Debug)]
enum Fold {
X(u32),
Y(u32),
}
#[derive(Debug)]
struct Page {
points: BTreeSet<Point>,
folds: Vec<Fold>,
}
impl Page {
fn do_next_fold(&mut self) -> bool {
let fold = self.folds.pop();
match fold {
Some(Fold::X(x)) => {
self.points = std::mem::take(&mut self.points)
.into_iter()
.filter(|point| point.x != x)
.map(|point| {
if point.x > x {
Point {
x: x - (point.x - x),
y: point.y,
}
} else {
point
}
})
.collect();
true
}
Some(Fold::Y(y)) => {
self.points = std::mem::take(&mut self.points)
.into_iter()
.filter(|point| point.y != y)
.map(|point| {
if point.y > y {
Point {
x: point.x,
y: y - (point.y - y),
}
} else {
point
}
})
.collect();
true
}
None => false,
}
}
fn count_points(&self) -> usize {
self.points.len()
}
}
impl fmt::Display for Page {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
let width = self.points.iter().map(|p| p.x).max().unwrap_or(0);
let height = self.points.iter().map(|p| p.y).max().unwrap_or(0);
for y in 0..=height {
for x in 0..=width {
let p = Point { x, y };
if self.points.contains(&p) {
write!(f, "#")?;
} else {
write!(f, ".")?;
}
}
writeln!(f)?;
}
Ok(())
}
}
fn parse_page(input: &str) -> IResult<&str, Page> {
let (input, points) = separated_list1(line_ending, parse_point)(input)?;
let (input, _) = many0(line_ending)(input)?;
let (input, mut folds) = separated_list1(line_ending, parse_fold)(input)?;
folds.reverse();
Ok((
input,
Page {
points: points.into_iter().collect(),
folds,
},
))
}
fn parse_fold(input: &str) -> IResult<&str, Fold> {
alt((
map(tuple((tag("fold along x="), nom_u32)), |(_, val)| {
Fold::X(val)
}),
map(tuple((tag("fold along y="), nom_u32)), |(_, val)| {
Fold::Y(val)
}),
))(input)
}
fn parse_point(input: &str) -> IResult<&str, Point> {
map(tuple((nom_u32, nom_char(','), nom_u32)), |(x, _, y)| {
Point { x, y }
})(input)
}
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