Update to Clap 3.0.0!

Turns out you can incorrectly implement the problem and still get the
right answer for part 1. If you then correct it, it's a lot faster.

2021/Cargo.toml

@@ -5,7 +5,7 @@ edition = "2021"
 
 
 [dependencies]
-clap = { version = "3.0.0-rc.0", features = ["derive"] }
+clap = { version = "3", features = ["derive"] }
 itertools = "0.10"
 nom = "7"
 

2021/src/common.rs

@@ -90,7 +90,49 @@ where
     let mut buffer = Vec::new();
     input.read_to_end(&mut buffer).unwrap();
 
-    let (_, output) = parser(&buffer).finish().unwrap();
-
-    output
+    match parser(&buffer).finish() {
+        Ok((_, output)) => output,
+        Err(err) => {
+            panic!(
+                "Failed to parse input with error {:?} at \"{}\"",
+                err.code,
+                String::from_utf8_lossy(err.input)
+            );
+        }
+    }
+}
+
+pub struct BitSet {
+    buffer: Vec<u32>,
+}
+
+impl BitSet {
+    pub fn new() -> Self {
+        Self::with_capacity(0)
+    }
+
+    pub fn with_capacity(capacity: usize) -> Self {
+        let buffer = Vec::with_capacity(capacity);
+
+        Self { buffer }
+    }
+
+    pub fn insert(&mut self, value: usize) -> bool {
+        let chunk = value / 32;
+        let bit = 1 << (31 - (value % 32));
+
+        if self.buffer.len() <= chunk + 1 {
+            self.buffer.resize(chunk + 1, 0);
+        }
+
+        let not_present = self.buffer[chunk] & bit;
+
+        self.buffer[chunk] |= bit;
+
+        not_present == 0
+    }
+
+    pub fn len(&self) -> usize {
+        self.buffer.iter().map(|c| c.count_ones() as usize).sum()
+    }
 }

2021/src/day05.rs

@@ -1,69 +1,91 @@
-use std::collections::HashMap;
 use std::io::Read;
 use std::iter::repeat;
 
 use nom::bytes::complete::tag;
-use nom::sequence::tuple;
-use nom::Finish;
+use nom::character::complete::newline;
+use nom::combinator::map;
+use nom::multi::separated_list1;
+use nom::sequence::separated_pair;
 use nom::IResult;
 
 use crate::common::ordered;
-use crate::common::LineIter;
+use crate::common::read_input;
+use crate::common::BitSet;
 
 type Coord = (u16, u16);
 
-fn coordinates(input: &str) -> IResult<&str, Coord> {
-    use nom::character::complete;
+fn coordinates(input: &[u8]) -> IResult<&[u8], Coord> {
+    use nom::character::complete::char;
+    use nom::character::complete::u16;
 
-    let (input, (x, _, y)) = tuple((complete::u16, complete::char(','), complete::u16))(input)?;
-
-    Ok((input, (x, y)))
+    separated_pair(u16, char(','), u16)(input)
 }
 
-fn line_definition(input: &str) -> IResult<&str, (Coord, Coord)> {
-    let (input, (begin, _, end)) = tuple((coordinates, tag(" -> "), coordinates))(input)?;
+fn parse_input(input: &[u8]) -> IResult<&[u8], Vec<(Coord, Coord)>> {
+    let read_line = map(
+        separated_pair(coordinates, tag(" -> "), coordinates),
+        |(begin, end)| ordered(begin, end),
+    );
 
-    // Sorting the coordinates saves trouble later
-    Ok((input, ordered(begin, end)))
+    separated_list1(newline, read_line)(input)
 }
 
 fn stripe(
-    map: &mut HashMap<Coord, u16>,
+    once: &mut BitSet,
+    twice: &mut BitSet,
+    width: usize,
     xs: impl Iterator<Item = u16>,
     ys: impl Iterator<Item = u16>,
 ) {
     for (x, y) in xs.zip(ys) {
-        *map.entry((x, y)).or_default() += 1;
+        let index = x as usize + y as usize * width;
+        if !once.insert(index) {
+            twice.insert(index);
+        }
     }
 }
 
 fn part_common(input: &mut dyn Read, diagonals: bool) -> String {
-    let mut reader = LineIter::new(input);
-    let mut map = HashMap::new();
+    let lines = read_input(input, parse_input);
 
-    while let Some(line) = reader.next() {
-        let (begin, end) = line_definition(line).finish().unwrap().1;
+    let width = lines.iter().map(|&((_, x_max), _)| x_max).max().unwrap() as usize + 1;
 
+    let mut once_map = BitSet::new();
+    let mut twice_map = BitSet::new();
+
+    for (begin, end) in lines {
         if begin.0 == end.0 {
             let y_range = begin.1..=end.1;
-            stripe(&mut map, repeat(begin.0), y_range);
+            stripe(
+                &mut once_map,
+                &mut twice_map,
+                width,
+                repeat(begin.0),
+                y_range,
+            );
         } else if begin.1 == end.1 {
             let x_range = begin.0..=end.0;
-            stripe(&mut map, x_range, repeat(begin.1));
+            stripe(
+                &mut once_map,
+                &mut twice_map,
+                width,
+                x_range,
+                repeat(begin.1),
+            );
         } else if diagonals {
             let x_range = begin.0..=end.0;
             let y_range = (begin.1.min(end.1))..=(begin.1.max(end.1));
 
             if begin.1 > end.1 {
                 // For a downward slope we need to reverse Y
-                stripe(&mut map, x_range, y_range.rev());
+                stripe(&mut once_map, &mut twice_map, width, x_range, y_range.rev());
             } else {
-                stripe(&mut map, x_range, y_range);
+                stripe(&mut once_map, &mut twice_map, width, x_range, y_range);
             }
         }
     }
 
-    map.values().filter(|&&v| v > 1).count().to_string()
+    twice_map.len().to_string()
 }
 
 pub fn part1(input: &mut dyn Read) -> String {
@@ -82,11 +104,6 @@ mod tests {
 
     const SAMPLE: &[u8] = include_bytes!("samples/05.txt");
 
-    #[test]
-    fn test_parser() {
-        assert_eq!(line_definition("6,4 -> 2,0"), Ok(("", ((2, 0), (6, 4)))));
-    }
-
     #[test]
     fn sample_part1() {
         test_implementation(part1, SAMPLE, 5)

2021/src/day16.rs

@@ -182,7 +182,7 @@ mod tests {
     fn sample_part1() {
         let answers = [16, 12, 23, 31];
 
-        for (&sample, answer) in SAMPLE.into_iter().zip(answers) {
+        for (&sample, answer) in SAMPLE.iter().zip(answers) {
             test_implementation(part1, sample, answer);
         }
     }

2021/src/day23.rs

@@ -1,9 +1,451 @@
+use std::cmp::Reverse;
+use std::collections::hash_map::Entry;
+use std::collections::BinaryHeap;
+use std::collections::HashMap;
+use std::fmt::Display;
 use std::io::Read;
+use std::mem::swap;
 
-pub fn part1(_input: &mut dyn Read) -> String {
-    todo!()
+use crate::common::LineIter;
+
+type Item<const S: usize> = (u32, State<S>);
+type Todo<const S: usize> = BinaryHeap<Reverse<Item<S>>>;
+type Visited<const S: usize> = HashMap<State<S>, u32>;
+
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Copy, Clone, Hash)]
+enum Pod {
+    A,
+    B,
+    C,
+    D,
 }
 
-pub fn part2(_input: &mut dyn Read) -> String {
-    todo!()
+impl Pod {
+    pub fn cost(self) -> u32 {
+        match self {
+            Pod::A => 1,
+            Pod::B => 10,
+            Pod::C => 100,
+            Pod::D => 1000,
+        }
+    }
+
+    pub fn dest(self) -> usize {
+        self as usize
+    }
+}
+
+impl TryFrom<usize> for Pod {
+    type Error = usize;
+
+    fn try_from(index: usize) -> Result<Self, Self::Error> {
+        match index {
+            0 => Ok(Pod::A),
+            1 => Ok(Pod::B),
+            2 => Ok(Pod::C),
+            3 => Ok(Pod::D),
+            _ => Err(index),
+        }
+    }
+}
+
+impl TryFrom<char> for Pod {
+    type Error = &'static str;
+
+    fn try_from(c: char) -> Result<Self, Self::Error> {
+        match c {
+            'A' => Ok(Pod::A),
+            'B' => Ok(Pod::B),
+            'C' => Ok(Pod::C),
+            'D' => Ok(Pod::D),
+            _ => Err("Invalid pod"),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Hash)]
+struct State<const S: usize> {
+    hallway: [Option<Pod>; 11],
+    rooms: [[Option<Pod>; S]; 4],
+}
+
+fn room_hallway_pos(room: usize) -> usize {
+    room * 2 + 2
+}
+
+fn abs_delta(a: usize, b: usize) -> usize {
+    if a < b {
+        b - a
+    } else {
+        a - b
+    }
+}
+
+impl<const S: usize> State<S> {
+    const VALID_HALLWAY_POS: [usize; 7] = [0, 1, 3, 5, 7, 9, 10];
+
+    pub fn is_done(&self) -> bool {
+        self == &State {
+            hallway: Default::default(),
+            rooms: [
+                [Some(Pod::A); S],
+                [Some(Pod::B); S],
+                [Some(Pod::C); S],
+                [Some(Pod::D); S],
+            ],
+        }
+    }
+
+    fn add_to_queue(self, cost: u32, todo: &mut Todo<S>, visited: &mut Visited<S>) {
+        let entry = visited.entry(self.clone());
+
+        if matches!(&entry, Entry::Occupied(entry) if *entry.get() <= cost) {
+            // Already got a better one
+            return;
+        }
+
+        // nightly only :'(
+        // entry.insert(cost);
+        *entry.or_default() = cost;
+
+        todo.push(Reverse((cost + self.estimate(), self)))
+    }
+
+    fn estimate(&self) -> u32 {
+        // A* estimate. For every entry that is not already "at rest", the cost is the cost
+        // required to get it to the top of its intended room.
+
+        // Cost to enter the hole for all pods that still need to
+        let enter_estimate: u32 = self
+            .rooms
+            .iter()
+            .enumerate()
+            .map(|(index, room)| {
+                let pod = Pod::try_from(index).unwrap();
+
+                room.iter()
+                    .enumerate()
+                    .rev()
+                    .skip_while(|&(_, &entry)| entry == Some(pod))
+                    .map(|(index, _)| index as u32 + 1)
+                    .sum::<u32>()
+                    * pod.cost()
+            })
+            .sum();
+
+        // Cost for all of the hallway to move to above their intended rooms
+        let hallway_estimate: u32 = self
+            .hallway
+            .iter()
+            .enumerate()
+            .filter_map(|(pos, &pod)| {
+                let pod = pod?;
+
+                let destination_pos = room_hallway_pos(pod.dest());
+
+                Some(abs_delta(pos, destination_pos) as u32 * pod.cost())
+            })
+            .sum();
+
+        // Cost to move out of the room and above the correct rooms
+        let rooms_estimate: u32 = self
+            .rooms
+            .iter()
+            .enumerate()
+            .map(|(room_index, room)| {
+                let hallway_pos = room_hallway_pos(room_index);
+
+                room.iter()
+                    .enumerate()
+                    .rev()
+                    .skip_while(|&(_, &entry)| {
+                        entry.map(|pod| pod.dest() == room_index).unwrap_or(false)
+                    })
+                    .filter_map(|(room_pos, &pod)| {
+                        let pod = pod?;
+
+                        let destination_pos = room_hallway_pos(pod.dest());
+
+                        let steps = 1 + room_pos + abs_delta(hallway_pos, destination_pos).max(2);
+
+                        Some(steps as u32 * pod.cost())
+                    })
+                    .sum::<u32>()
+            })
+            .sum();
+
+        enter_estimate + hallway_estimate + rooms_estimate
+    }
+
+    pub fn generate_next(&self, cost: u32, todo: &mut Todo<S>, visited: &mut Visited<S>) {
+        self.room_to_hallway(cost, todo, visited);
+        self.hallway_to_room(cost, todo, visited);
+    }
+
+    fn room_to_hallway(&self, cost: u32, todo: &mut Todo<S>, visited: &mut Visited<S>) {
+        for (index, room) in self.rooms.iter().enumerate() {
+            // Check if we even want to move anything out of this room
+            if room
+                .iter()
+                .all(|entry| entry.map(|pod| pod.dest() == index).unwrap_or(true))
+            {
+                continue;
+            }
+
+            let (pos, pod) = room
+                .iter()
+                .enumerate()
+                .find_map(|(pos, entry)| entry.map(|pod| (pos, pod)))
+                .unwrap(); // Safe unwrap, we know it exists from above.
+
+            let base_cost = 1 + pos;
+            let hallway_pos = room_hallway_pos(index);
+
+            let mut queue_new = |new_pos, new_cost| {
+                let mut new_state = self.clone();
+                swap(
+                    &mut new_state.hallway[new_pos],
+                    &mut new_state.rooms[index][pos],
+                );
+
+                new_state.add_to_queue(new_cost + cost, todo, visited)
+            };
+
+            // Check positions to the left
+            for new_pos in (0..hallway_pos).rev() {
+                if self.hallway[new_pos].is_some() {
+                    // Hit an occupied room
+                    break;
+                }
+
+                if !Self::VALID_HALLWAY_POS.contains(&new_pos) {
+                    // Not allowed to stop here
+                    continue;
+                }
+
+                let new_cost = (base_cost + hallway_pos - new_pos) as u32 * pod.cost();
+                queue_new(new_pos, new_cost);
+            }
+
+            // And to the right
+            for new_pos in hallway_pos..self.hallway.len() {
+                if self.hallway[new_pos].is_some() {
+                    // Hit an occupied room
+                    break;
+                }
+
+                if !Self::VALID_HALLWAY_POS.contains(&new_pos) {
+                    // Not allowed to stop here
+                    continue;
+                }
+
+                let new_cost = (base_cost + new_pos - hallway_pos) as u32 * pod.cost();
+                queue_new(new_pos, new_cost);
+            }
+        }
+    }
+
+    fn hallway_to_room(&self, cost: u32, todo: &mut Todo<S>, visited: &mut Visited<S>) {
+        for (pos, pod) in self
+            .hallway
+            .iter()
+            .enumerate()
+            .filter_map(|(pos, pod)| pod.map(|pod| (pos, pod)))
+        {
+            let room = pod.dest();
+            let new_hallway_pos = room_hallway_pos(room);
+
+            // Check if the path is free
+            let in_between = if new_hallway_pos < pos {
+                &self.hallway[(new_hallway_pos + 1)..pos]
+            } else {
+                &self.hallway[(pos + 1)..new_hallway_pos]
+            };
+
+            if in_between.iter().any(Option::is_some) {
+                // Something's in the way
+                continue;
+            }
+
+            // Check if we can move into the room
+            if self.rooms[room]
+                .iter()
+                .copied()
+                .flatten()
+                .any(|other| other != pod)
+            {
+                // Scared of other pods
+                continue;
+            }
+
+            let room_pos = if let Some(pos) = self.rooms[room].iter().rposition(Option::is_none) {
+                pos
+            } else {
+                continue;
+            };
+
+            let new_cost = (abs_delta(pos, new_hallway_pos) + room_pos + 1) as u32 * pod.cost();
+            let mut new_state = self.clone();
+            swap(
+                &mut new_state.hallway[pos],
+                &mut new_state.rooms[room][room_pos],
+            );
+            new_state.add_to_queue(cost + new_cost, todo, visited);
+        }
+    }
+
+    pub fn solve(&self) -> u32 {
+        let mut todo = Todo::new();
+
+        let mut visited = HashMap::new();
+        visited.insert(self.clone(), 0);
+
+        todo.push(Reverse((self.estimate(), self.clone())));
+
+        while let Some(Reverse((_, state))) = todo.pop() {
+            let cost = *visited.get(&state).unwrap_or(&0);
+
+            if state.is_done() {
+                return cost;
+            }
+
+            state.generate_next(cost, &mut todo, &mut visited);
+        }
+
+        panic!("No route found!")
+    }
+}
+
+impl<const S: usize> Display for State<S> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let helper = |opt_pod| match opt_pod {
+            Some(Pod::A) => 'A',
+            Some(Pod::B) => 'B',
+            Some(Pod::C) => 'C',
+            Some(Pod::D) => 'D',
+            None => '.',
+        };
+        writeln!(f, "#############")?;
+        write!(f, "#")?;
+
+        for entry in self.hallway {
+            write!(f, "{}", helper(entry))?;
+        }
+        writeln!(f, "#")?;
+
+        for i in 0..S {
+            writeln!(
+                f,
+                "  #{}#{}#{}#{}#",
+                helper(self.rooms[0][i]),
+                helper(self.rooms[1][i]),
+                helper(self.rooms[2][i]),
+                helper(self.rooms[3][i])
+            )?;
+        }
+
+        write!(f, "  #########")
+    }
+}
+
+fn read_input(input: &mut dyn Read) -> State<2> {
+    let mut reader = LineIter::new(input);
+    let mut state = State {
+        hallway: Default::default(),
+        rooms: Default::default(),
+    };
+
+    let _ = reader.next();
+    let _ = reader.next();
+
+    let mut helper = |idx: usize| {
+        reader
+            .next()
+            .unwrap()
+            .chars()
+            .filter_map(|c| Pod::try_from(c).ok())
+            .zip(&mut state.rooms)
+            .for_each(|(pod, room)| room[idx] = Some(pod))
+    };
+
+    helper(0);
+    helper(1);
+
+    state
+}
+
+pub fn part1(input: &mut dyn Read) -> String {
+    let state = read_input(input);
+
+    state.solve().to_string()
+}
+
+pub fn part2(input: &mut dyn Read) -> String {
+    let state2 = read_input(input);
+
+    let state4 = State {
+        hallway: Default::default(),
+        rooms: [
+            [
+                state2.rooms[0][0],
+                Some(Pod::D),
+                Some(Pod::D),
+                state2.rooms[0][1],
+            ],
+            [
+                state2.rooms[1][0],
+                Some(Pod::C),
+                Some(Pod::B),
+                state2.rooms[1][1],
+            ],
+            [
+                state2.rooms[2][0],
+                Some(Pod::B),
+                Some(Pod::A),
+                state2.rooms[2][1],
+            ],
+            [
+                state2.rooms[3][0],
+                Some(Pod::A),
+                Some(Pod::C),
+                state2.rooms[3][1],
+            ],
+        ],
+    };
+
+    state4.solve().to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::test_implementation;
+
+    const SAMPLE: &[u8] = include_bytes!("samples/23.txt");
+
+    #[test]
+    fn test_is_done() {
+        let state = State {
+            hallway: Default::default(),
+            rooms: [
+                [Some(Pod::A); 2],
+                [Some(Pod::B); 2],
+                [Some(Pod::C); 2],
+                [Some(Pod::D); 2],
+            ],
+        };
+
+        assert!(state.is_done());
+    }
+
+    #[test]
+    fn sample_part1() {
+        test_implementation(part1, SAMPLE, 12521);
+    }
+
+    #[test]
+    fn sample_part2() {
+        test_implementation(part2, SAMPLE, 44169);
+    }
 }

2021/src/day24.rs

@@ -1,9 +1,159 @@
+//! Very input-specific reverse-engineered solution
+//!
+//! # General implementation
+//!
+//! The code in the examples is a series of 14 times this:
+//!
+//! ```txt
+//! inp w       -> read digit
+//! mul x 0
+//! add x z
+//! mod x 26    -> x = z % 26
+//! div z $A    -> pop Z (see below)
+//! add x $B
+//! eql x w     -> x = ((z + $B) == w)
+//! eql x 0     -> x = ((z + $B) != w)
+//! mul y 0
+//! add y 25
+//! mul y x
+//! add y 1     -> if x { 26 } else { 1 }
+//! mul z y     -> if x { z *= 26 } (push z, see below)
+//! mul y 0
+//! add y w
+//! add y $C    -> y = w + $C
+//! mul y x
+//! add z y     -> if x { z += w + $C }
+//! ```
+//!
+//! `$A` is either `1` or `26` which we can translate to a bool `$A == 26` for convenience. This
+//! simplifies to the following rust.
+//!
+//! ```
+//! fn validate<const A: bool, const B: i32, const C: i32>(mut z: i32, digit: i32) -> i32 {
+//!     let x = (z % 26 + B) != digit;
+//!     if A {
+//!         z /= 26;
+//!     }
+//!
+//!     if x {
+//!         z = 26 * z + digit + C;
+//!     }
+//!
+//!     z
+//! }
+//! ```
+//!
+//! In human terms, `z` is used to hold a base 26 number. When `$A` is `true`, we pop off the least
+//! significant digit by dividing by 26. Then, depending on whether `(z + $B) % 26` is equal to our
+//! digit, we push `digit + $C`. Ideally, we should pop as often as we push in order to arrive at `z
+//! == 0` in the end. The input contains 7 pops, so we want each of those to not push.
+//!
+//! To solve this problem, we use a backtracking memoizing algorithm, where we cancel every sequence
+//! that fails to pop at some point. A pop is failed whenever we execute a validation pop where we
+//! can pop if `x` happened to be set to `0` at the time of the check. We can memoize this over the
+//! running value of `z`.
+//!
+//! This implementation probably doesn't work on other people's input; to fix it, you'll want to
+//! update the `parse_step` function. Good luck with that.
+use std::collections::HashMap;
 use std::io::Read;
 
-pub fn part1(_input: &mut dyn Read) -> String {
-    todo!()
+use nom::branch::alt;
+use nom::bytes::complete::tag;
+use nom::character::complete::newline;
+use nom::combinator::map;
+use nom::multi::separated_list1;
+use nom::sequence::delimited;
+use nom::sequence::preceded;
+use nom::sequence::tuple;
+use nom::IResult;
+
+use crate::common::read_input;
+
+type Cache = HashMap<(usize, i32), Option<i64>>;
+
+#[derive(Debug)]
+struct Step(bool, i32, i32);
+
+impl Step {
+    fn evaluate(&self, digit: i32, z: i32) -> Option<i32> {
+        if self.0 {
+            (z % 26 + self.1 == digit).then(|| z / 26)
+        } else {
+            Some(z * 26 + digit + self.2)
+        }
+    }
 }
 
-pub fn part2(_input: &mut dyn Read) -> String {
-    todo!()
+fn parse_step(input: &[u8]) -> IResult<&[u8], Step> {
+    use nom::character::complete::i32;
+
+    let parse_pop = preceded(
+        tag("inp w\nmul x 0\nadd x z\nmod x 26\ndiv z "),
+        alt((map(tag("1"), |_| false), map(tag("26"), |_| true))),
+    );
+
+    let parse_a = preceded(tag("\nadd x "), i32);
+
+    let parse_b = delimited(
+        tag("\neql x w\neql x 0\nmul y 0\nadd y 25\nmul y x\nadd y 1\nmul z y\nmul y 0\nadd y w\nadd y "),
+        i32,
+        tag("\nmul y x\nadd z y"),
+    );
+
+    map(tuple((parse_pop, parse_a, parse_b)), |(pop, a, b)| {
+        Step(pop, a, b)
+    })(input)
+}
+
+fn parse_input(input: &[u8]) -> IResult<&[u8], Vec<Step>> {
+    separated_list1(newline, parse_step)(input)
+}
+
+fn optimize(
+    current: usize,
+    steps: &[Step],
+    digits: &[i32],
+    z: i32,
+    cache: &mut Cache,
+) -> Option<i64> {
+    if current >= steps.len() {
+        return (z == 0).then(|| 0);
+    }
+
+    if let Some(&memoized) = cache.get(&(current, z)) {
+        return memoized;
+    }
+
+    let result = digits.iter().find_map(|&digit| {
+        let z = steps[current].evaluate(digit, z)?;
+        let result = optimize(current + 1, steps, digits, z, cache)?;
+
+        Some(result + digit as i64 * 10i64.pow(13 - current as u32))
+    });
+    cache.insert((current, z), result);
+
+    result
+}
+
+fn parts_common(input: &mut dyn Read, digits: &[i32]) -> String {
+    let steps = read_input(input, parse_input);
+
+    let mut cache = Cache::new();
+
+    optimize(0, &steps, digits, 0, &mut cache)
+        .unwrap()
+        .to_string()
+}
+
+pub fn part1(input: &mut dyn Read) -> String {
+    let digits = [9, 8, 7, 6, 5, 4, 3, 2, 1];
+
+    parts_common(input, &digits)
+}
+
+pub fn part2(input: &mut dyn Read) -> String {
+    let digits = [1, 2, 3, 4, 5, 6, 7, 8, 9];
+
+    parts_common(input, &digits)
 }

2021/src/lib.rs

@@ -92,7 +92,7 @@ pub fn get_implementation(day: usize, part2: bool) -> Solution {
 
 #[cfg(test)]
 fn test_implementation(solution: Solution, data: &[u8], answer: impl ToString) {
-    let result = solution(&mut &data[..]);
+    let result = solution(&mut &*data);
 
     assert_eq!(answer.to_string(), result);
 }

2021/src/samples/23.txt

@@ -0,0 +1,5 @@
+#############
+#...........#
+###B#C#B#D###
+  #A#D#C#A#
+  #########