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-rw-r--r--day20/Cargo.toml9
-rw-r--r--day20/resources/input.txt102
-rw-r--r--day20/src/main.rs138
3 files changed, 249 insertions, 0 deletions
diff --git a/day20/Cargo.toml b/day20/Cargo.toml
new file mode 100644
index 0000000..6696ef0
--- /dev/null
+++ b/day20/Cargo.toml
@@ -0,0 +1,9 @@
1[package]
2name = "day20"
3version = "0.1.0"
4authors = ["Federico Igne <git@federicoigne.com>"]
5edition = "2018"
6
7# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
8
9[dependencies]
diff --git a/day20/resources/input.txt b/day20/resources/input.txt
new file mode 100644
index 0000000..3fec6c5
--- /dev/null
+++ b/day20/resources/input.txt
@@ -0,0 +1,102 @@
1###.#..##.#...#.##.#..#...#####..###....###..##..####.#..#.##.#.#...##.##.##.#...#....##..#..####...####..######..#.##..###......#..##.##.##...###.#..#.#.##.##.#..#####....####...#..##.###.#....#..#..#..###.#.#.##.#.#.#.######...#.###..####.....##..#..#.#....#.####.##.##..#.##.....##...#..#.#..####.##.#..#..#.###.##....##.#..........###.#..#.....#.##.##......##.....##...#........#.#......###...#####....##.#.#..###...#.#.###.##.#..#..###.#......#......####..#.#.##..#..#...####.#.#.#.#...#.####....##.###.....
2
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diff --git a/day20/src/main.rs b/day20/src/main.rs
new file mode 100644
index 0000000..a11d49a
--- /dev/null
+++ b/day20/src/main.rs
@@ -0,0 +1,138 @@
1use std::fs;
2use std::path::Path;
3use std::collections::VecDeque;
4use std::fmt::Display;
5use std::fmt::Formatter;
6use std::fmt::Result;
7
8#[derive(Debug)]
9struct Map {
10 step: usize,
11 pixels: VecDeque<VecDeque<u8>>
12}
13
14impl Map {
15 fn pad(&mut self, pix: u8) {
16 let h = self.pixels.len();
17 let w = self.pixels[0].len();
18 let pix = if pix == 0 { 0 } else { u8::MAX };
19 if self.pixels[h-1].iter().any(|&b| b > 0) || self.pixels[h-2].iter().any(|&b| b > 0) {
20 let empty = VecDeque::from([pix].repeat(w));
21 self.pixels.push_back(empty.clone());
22 self.pixels.push_back(empty);
23 }
24 if self.pixels[0].iter().any(|&b| b > 0) || self.pixels[1].iter().any(|&b| b > 0) {
25 let empty = VecDeque::from([pix].repeat(w));
26 self.pixels.push_front(empty.clone());
27 self.pixels.push_front(empty);
28 }
29 if self.pixels.iter().any(|v| v[w-1] & 3 != 0) {
30 self.pixels.iter_mut().for_each(|v| v.push_back(pix));
31 }
32 if self.pixels.iter().any(|v| v[0] >= (1<<6)) {
33 self.pixels.iter_mut().for_each(|v| v.push_front(pix));
34 }
35 }
36
37 fn enhance(mut self, algorithm: &[u8]) -> Map {
38 let padpix = if algorithm[0] == 0 { 0 } else { algorithm[[algorithm.len()-1,0][self.step % 2]] };
39 self.pad(padpix);
40 let h = self.pixels.len();
41 let w = self.pixels[0].len();
42 let mut pixels = VecDeque::with_capacity(h);
43 for i in 0..h {
44 let mut row = VecDeque::with_capacity(w);
45 for j in 0..w {
46 let mut byte = 0;
47 for p in 0..8 {
48 let pix = {
49 if i < 1 || i > h-2 || (j < 1 && p < 1 ) || (j > w-2 && p > 6) {
50 if algorithm[0] == 0 { 0 } else { algorithm[[0,algorithm.len()-1][self.step % 2]] }
51 } else {
52 algorithm[self.index(i,8*j+p)]
53 }
54 };
55 byte = (byte<<1) | pix;
56 }
57 row.push_back(byte);
58 }
59 pixels.push_back(row);
60 }
61 Map { step: self.step+1, pixels }
62 }
63
64 fn pix(&self, y: usize, x: usize) -> u8 {
65 (self.pixels[y][x/8] >> (7-x%8)) & 1
66 }
67
68 fn index(&self, y: usize, x: usize) -> usize {
69 let mut idx = 0;
70 for i in y-1..y+2 {
71 for j in x-1..x+2 {
72 idx = (idx << 1) | self.pix(i,j) as usize
73 }
74 }
75 idx
76 }
77
78 fn lights(&self) -> u32 {
79 self.pixels.iter().flat_map(|v| v.iter().map(|&b| b.count_ones())).sum()
80 }
81}
82
83impl Display for Map {
84 fn fmt(&self, f: &mut Formatter<'_>) -> Result {
85 self.pixels.iter().for_each(|v| {
86 v.iter().for_each(|b| write!(f, "{}", format!("{:08b}",b).chars().map(|c| if c == '1' { '#' } else { '.' }).collect::<String>()).unwrap());
87 write!(f, "\n").unwrap()
88 });
89 Ok(())
90 }
91}
92
93fn main() {
94 let input = Path::new("resources").join("input.txt");
95 let content = fs::read_to_string(input).expect("Unable to read input file");
96 let (mut map, algorithm) = parse_input(&content);
97 map = map.enhance(&algorithm).enhance(&algorithm);
98 println!("Ex1: The result is {}", map.lights());
99 for _ in 0..50-2 {
100 map = map.enhance(&algorithm);
101 }
102 println!("Ex2: The result is {}", map.lights());
103}
104
105fn parse_input(input: &str) -> (Map, Vec<u8>) {
106 let (algorithm,pixels) = input.split_once("\n\n").expect("Malformed input");
107 let algorithm: Vec<u8> = algorithm.chars().map(|c| (c == '#') as u8).collect();
108 let pixels: VecDeque<VecDeque<u8>> = pixels.lines().map(|l| {
109 let bits: Vec<u8> = l.chars().map(|c| (c == '#') as u8).collect();
110 bits.chunks(8).map(|c| c.iter().fold(0, |a,b| (a<<1)|b) << (8-c.len())).collect()
111 }).collect();
112 (Map { step: 0, pixels }, algorithm)
113}
114
115#[cfg(test)]
116mod tests {
117 use super::*;
118
119 const INPUT: &str = "..#.#..#####.#.#.#.###.##.....###.##.#..###.####..#####..#....#..#..##..###..######.###...####..#..#####..##..#.#####...##.#.#..#.##..#.#......#.###.######.###.####...#.##.##..#..#..#####.....#.#....###..#.##......#.....#..#..#..##..#...##.######.####.####.#.#...#.......#..#.#.#...####.##.#......#..#...##.#.##..#...##.#.##..###.#......#.#.......#.#.#.####.###.##...#.....####.#..#..#.##.#....##..#.####....##...##..#...#......#.#.......#.......##..####..#...#.#.#...##..#.#..###..#####........#..####......#..#
120
121#..#.
122#....
123##..#
124..#..
125..###";
126
127 #[test]
128 fn input_parse() {
129 let (mut map,algorithm) = parse_input(INPUT);
130 println!("{}", map);
131 map = map.enhance(&algorithm);
132 println!("{}", map);
133 map = map.enhance(&algorithm);
134 println!("{}", map);
135 assert_eq!(35, map.lights());
136
137 }
138}
generated by cgit v1.2.3 (git 2.25.1) at 2025-07-08 21:54:40 +0000