Year 2016: Day 24

CHANGELOG.md

@@ -10,11 +10,14 @@ Of note:
 - The changelog 2015.5.2 has been rewritten from each commit content.
 - This file may be amended entirely in the future to adhere to the [GNU Changelog style](https://www.gnu.org/prep/standards/html_node/Style-of-Change-Logs.html#Style-of-Change-Logs)
 
+## [2016.24.1]
+### Added
+- Solved [exercice for 2016, day 24](src/year_2016/24.rs).
+
 ## [2016.23.1]
 ### Added
 - Solved [exercice for 2016, day 23](src/year_2016/23.rs).
 
-
 ## [2016.22.1]
 ### Added
 - Solved [exercice for 2016, day 22](src/year_2016/22.rs).

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "advent-rs"
-version = "2016.23.1"
+version = "2016.24.1"
 edition = "2021"
 authors = ["Arnaud 'red' Rouyer"]
 readme = "README.md"

NOTES_2016.md

@@ -106,3 +106,7 @@ So far, my [BreadthFirstSearch library](src/bfs.rs) has saved me from rewriting
 ## Day 23: Safe Cracking
 
 I had forgotten [the original was taking ten minutes to run](https://github.com/joshleaves/advent-rb/NOTES_2016.md#day-23-safe-cracking). This one takes only seven seconds, and I'll be happy with it.
+
+## Day 24: Air Duct Spelunking
+
+Look, [BreadthFirstSearch library](src/bfs.rs) is coming to our rescue again!

README.md

@@ -6,7 +6,7 @@ As I said, [Consistency is hard](https://github.com/joshleaves/advent-rb), and I
 
 I'm also adding notes that may be useful if you're (like me) discovering Rust:
 - [2015, complete!](NOTES_2015.md)
-- [2016, up to day 23](NOTES_2016.md)
+- [2016, up to day 24](NOTES_2016.md)
 
 # Regarding style rules
 I'm gonna use a mix of what `cargo fmt` does, with some stuff that feels more natural to me.

inputs/year_2016/day_24_input

@@ -0,0 +1,39 @@
+#####################################################################################################################################################################################
+#.....#.#.....#.#.#...#.....#.#.#.#.....#3......#...........#.#.....#.....#.............#.#...#...#.....#...#.........#.#...............#.....#.....#.........................#.....#
+#.#.#.#.#.#.#.#.#.#.#.#.###.#.#.#.#.#.#####.#.#.#.#####.#.###.#.#.###.#.#####.###.#.#.#.#.#####.#.#.#.#####.#.#.#####.#.#.#####.###.#.#.###.###.###.#.###.#.###.###.#.#######.#######
+#.....#...#.#.....#...#.........#...........#.......#...#.#.....#.....#.#.#.......#...#.#...#...#...#.#...#...#.#...#.#.#.#.......#...#...#.....#.....#.....#...#...#.......#.#...#.#
+###.#####.#.#######.###.#.#.#.#.#.#####.#.#.#.#####.#.###.#.#####.#.#.#.#.#####.#.#.#.#.#.###.#.###.#.#####.#.#.#.#.###.#.#.#.###.#.#.#.#.###.#.#.###.#.#.#.#.#.#.#.#.#.#####.#.#.#.#
+#...#1......#.....#.#.#.#.....#.#.#.....#...#.#...#.......#...........#.............#...#.....#.......#.....#.....#.#.......#.#...#.#.#.#.......#...#.#...........#.#.....#...#.#...#
+#.#.###.#.###.#.#.#.#.#.#.#######.#.#.###.#.#.#.###.#####.###.#.#.#.#.#.###.#.#####.#.#.#####.#####.#.#.#.#.#.#.#.###.###.#.#####.#.#.#####.#.#.#.#.#.#.#.###.#####.###.#.#.#.#.###.#
+#.....#.#.....#.#...#.#.....#.#.#.#.........#.#.#.......#.#.#.......#...#...#...#.....#.#...#.......#.....#.......#...#.....#...#...#.......#...#.#.....#...#.#.....#.#...#.#...#...#
+#.#.#.#.#####.#.###.#.#.#.###.#.###.#.#.#####.#.#####.#.#.#.#.#####.#.#.#.###.#######.#.###.#.###.#.#.#.#.#.#.#####.###.#####.#.#.#.#.#####.#####.#.###.#.#.#.#.#.#.#.#####.###.#.###
+#...#.#...#.........#.#...#.#...#.....#.#.....#.......#.........#.....#.....#.........#.....#...#.#.#.#.....#.#.................#.#.#.......#.......#.......#...#...#.......#.#...#.#
+#.#.#.#.#.#.#.###.#.###.###.#.#.#.###.###.#.#.#.#.#.#.#########.#.###.#.#.#####.#.#.#.###.#######.#.###.#.#.#.#.#.#.#.###.#.#.###.#######.#.###.#.#.#.#.###.#.#.#.#####.###.#.#.###.#
+#...#.#.#.#.#...#...#...#.............#.....#.....#...#...#.#.....#...#...#.....#.#.....#...#...........#.#.#.#.......#...#.............#...#.#...#...........#...#2#...#.....#.#.#.#
+###.###.#.#####.#.#.#.#.#.#.#.#.#.#.###.###.#.#.#.###.###.#.#.#.#.#.#.###.###.#.#.#.#.###.#.#.#.###.#####.###.###.#.#.#.###.#######.###.###.#.#.#.#####.#####.###.#.#.#####.#.#.#.###
+#.......#...#...........#.......#...#.#.......#.....#.....#...#...#.#.........#.......#...#.#...#...........#.#...#.#...............#.#.#.....#.......#.#.#.#.....#.........#.#.#.#.#
+###.#.#.#.#.#.#.#####.###.#.#.#.#.#.#.#.#.#.#.#.#.#.#.#####.#.###.#.###.#.#.#.#########.###.#.###.#.###.#.#.#.#.#######.#####.###.#.#.#.#.#####.#####.#.#.#.#.#.#######.#.###.#.#.#.#
+#...#.....#.#.............#...#.#.....#.#...#.......#.........#...#...#.#...#...........#...#...........#...#...#.................#...#.#.#.....#.......#.#.#.......#...#...#...#...#
+###.#.#######.#.#.#.###.#.#.#.###.#.#.#.#.#.###.#####.#.###.#.#.#.###.#.#.#.#.#.#.#.###.#.#.#.#.#.#.#####.#.#####.#.#.#.#.#.#######.#.#.#.###.#.#.#.#.#.###.#.###.#########.###.#.#.#
+#.....#...#.....#.....#...#.........#.#...#.....#...#.................#...#.#.#.......#.....#...#.#.................#.#.#.........#.....#...#.#...#.....#.................#.#.....#.#
+#.#####.#.#.#####.###.#.#.#.###.###.#.#########.#.#######.###.###.#.#.#.#.#.#.#.###.#.#.#####.#.###.#.#########.#.###.###.#.###.###.#.#.#.#.#.###.#####.#.#.#######.#.###.#.#.###.###
+#0#...#.#...#...........#.#.............#.#.......#.....#.#.#.....#.#.#...#.....#.#.#.......#.#...#.................#.#.#.....#...#.#.........#.......#.#...#.......#.......#.....#.#
+#####.#.###.#.#.###.#####.###.#######.###.#.#.###.#.#.#.#.#.#.#.#.###.#.#.#.#.#.#.#.#.#####.###.#.#####.#.#.#.###.#.#.#.#########.#.#.#.###.#.#.###.#.#####.#.#.#.#.#.###.###.#.#.#.#
+#...#.#.....#.#.#...#.......#.#.#...#.........#.......#...#.#.....#.............#...........#...#.#.......#.#.....#.#...........#...#.........#.#...#.#.....#.......#...#.......#...#
+###.###.###.#.###.###.#.###.###.#.#.#.#########.#####.###.#######.#.###.#.#.#.###.#.#.#.#.#.#.#.#####.###.#.#.#.#.#.#.#####.###.#.#.###.#####.#.#.#####.#.#.###.#.#####.#.#.#.#.#.#.#
+#.......#...............#.....#...#...#.#...#.........#...........#.....#.....#.......#...#.....#.......#.#.#.#...#...............#.....#.....#...#.#...#...#.#.#.#.#.....#...#.#.#4#
+#.#.#.#.#.#####.###.#.#####.#.###.#.###.#.#.#.###.###.#.#####.#.#####.#.#######.#.#####.#.#######.#.###.#.#.#.###.###.###.#####.#.###.#.#.#.#####.#.#.#.###.#.#.###.###.#.#.#.#.#.###
+#...#...........#.......#...#.....#.#.......#.....#.........#.#.......#.#...#...#...........#.......#.....#...#...#...#.#...#.....#...#.........#...#...#.....#.....#...#...#...#...#
+###.#.###.#############.#.###.###.#.###.#.#.#.#.#.#.#.#.###.#####.#.#.#.#.#.#####.###.#.#.#.#.###.#.#.#.#.#.###.#.#.###.#.#.#.###.###.#.#.###.#.#.#.#.#.#.#####.#.#.#.#.#.#.###.#.###
+#...#.....#.#...#.#.#.#...........#.......#...#.....#...#...................#...#...#.#.#.#...#.......#...............#...#...#...#...#.#.#5#...#...#.#...#...#.#...#.#...#...#.#...#
+#.###.###.#.#.#.#.#.#.###.#.#######.#.#.#.###.#.#.#.#.#.#.###.#.###.###.#.#.#.#.#.###.#.#.#.#.#.###.#.#.###.#.#.###.#.#.#.#.#.#.#.#.#####.#.#.#######.#.#.#.#.#.#####.#.#######.#.#.#
+#.........#.#...#.#...#...#.............#.....#...#.#.#.#.#.#.....#.#...#.....#.#.#.........#.....#.........#.....#...........#...#.........#.....#...#.#.#.#...#...........#...#...#
+#.#.#.#######.#.#####.#.#.#.###.#.#######.#####.#.#.###.#.#.#.###.###.#.###.#.#.#.###.#.#.#.#####.#.###.#.#.#.#.#.#.#####.#.#.###.#.#.#.#.#####.###.#####.#.#.#.#.###.#.#.#####.#####
+#...#...............#.#.......#.......#.......#.........#.#.#.#...#...#...#.......#.#.....#.#...........#...#.#.#...........#.#...#.......#.........#...#...#.....#...#.#.....#.#...#
+###.#.#.#.#.#########.#.#.#.#.#.#####.#.#######.#.###.#.#.#.###.###.#.#.#.#.#.###.#.#.###.#.#####.#.###########.#.#.#####.#####.#####.#####.#.#.#.#.#.#.#####.#.#.#########.#.###.#.#
+#.#...#.....#.......#.....#...#.......#.#.#...#...#...#.........#...#...#.#...#.#.........#.#.......#.#.#...#...#.........#.#.........#.....#.#.#...#.......#.#.....#.......#.#.....#
+#.#.###.#.###.#.#.#.#.###.#########.#.#.#.#.#.#.###.#.#.#####.#.#.#####.#####.#.#.#########.#.#.#.###.#.#####.#.#.###.###.#.#.#.#.#.#####.###.#.###########.#.#.#.#.#.#######.#####.#
+#........7#.....#.#...#.#.#.#.........#...#.#...........#.....#.......#.........#.........#.....#.......#.#.......#.#.#...#...#.#.#....6#.#.........................#...#.#.......#.#
+#.###.#.###.###.###.#.#.###.###.#####.###.#.#.###.#####.###.#.###.#.#.#.#.#.#.#.#.#####.#.#.#####.#######.#.###.#.#.#####.#####.#.#.#.###.#.#.#.#.#####.#.#.###.#####.#.#.#.#.#.#.#.#
+#.#...#.#...#.#.....#.#.......#...#.....#...#...#...#...#.#.....#...#.#...#...#...#.#.............#.............#.#...#.............#.#.....#.....#.......#.#.#.#.........#...#...#.#
+#####################################################################################################################################################################################

src/bfs.rs

@@ -61,6 +61,11 @@ where
     self
   }
 
+  pub fn shortest_path_to(&mut self, target_position: POS) -> usize {
+    self.traverse_until_position(target_position.clone());
+    self.depth
+  }
+
   pub fn traverse_until_depth(&mut self, target_depth: usize) -> &mut Self {
     self.traverse(|_position, depth| depth > target_depth, true)
   }

src/year_2016.rs

@@ -26,6 +26,7 @@ pub mod day_20;
 pub mod day_21;
 pub mod day_22;
 pub mod day_23;
+pub mod day_24;
 
 pub fn solve(day: u8, part: u8, input: impl Into<String>) -> Option<String> {
   if part != 1 && part != 2 {
@@ -56,6 +57,7 @@ pub fn solve(day: u8, part: u8, input: impl Into<String>) -> Option<String> {
     21 => Some(format!("{}", day_21::day_21(part, input))),
     22 => Some(format!("{}", day_22::day_22(part, input))),
     23 => Some(format!("{}", day_23::day_23(part, input))),
+    24 => Some(format!("{}", day_24::day_24(part, input))),
     _ => None,
   }
 }
@@ -234,4 +236,11 @@ mod tests {
     assert_eq!(day_23::day_23_v1(input), 13_776);
     assert_eq!(day_23::day_23_v2(input), 479_010_336);
   }
+
+  #[test]
+  fn day_24() {
+    let input = include_str!("../inputs/year_2016/day_24_input");
+    assert_eq!(day_24::day_24_v1(input), 430);
+    assert_eq!(day_24::day_24_v2(input), 700);
+  }
 }

src/year_2016/day_24.rs

@@ -0,0 +1,190 @@
+use crate::bfs::BreadthFirstSearch;
+use itertools::Itertools;
+use std::collections::HashMap;
+
+struct Labyrinth {
+  width: usize,
+  height: usize,
+  cells: Vec<bool>,
+  numbers: Vec<(usize, usize)>,
+}
+
+impl Labyrinth {
+  fn new(input: &str) -> Self {
+    let height = input.lines().count();
+    let width = input.lines().next().unwrap().len();
+    let mut nums = vec![];
+    let mut cells = vec![true; height * width];
+    for (y, line) in input.lines().enumerate() {
+      for (x, character) in line.chars().enumerate() {
+        match character {
+          '.' => (),
+          '#' => cells[y * width + x] = false,
+          '0'..='9' => nums.push((character as u8 - 48, (x, y))),
+          _ => panic!("Invalid character: {}", character),
+        }
+      }
+    }
+    nums.sort_by_key(|elt| elt.0);
+    let numbers = nums.iter().map(|elt| elt.1).collect();
+    Labyrinth {
+      width,
+      height,
+      cells,
+      numbers,
+    }
+  }
+
+  pub fn next_moves(&self, position: (usize, usize)) -> Vec<(usize, usize)> {
+    let mut results = vec![];
+    if position.0 > 0 && self.cells[position.1 * self.width + (position.0 - 1)] {
+      results.push((position.0 - 1, position.1));
+    }
+    if position.0 < self.width && self.cells[position.1 * self.width + (position.0 + 1)] {
+      results.push((position.0 + 1, position.1));
+    }
+
+    if position.1 > 0 && self.cells[(position.1 - 1) * self.width + position.0] {
+      results.push((position.0, position.1 - 1));
+    }
+    if position.1 < self.height && self.cells[(position.1 + 1) * self.width + position.0] {
+      results.push((position.0, position.1 + 1));
+    }
+    results
+  }
+}
+
+#[inline]
+fn get_distance(distances: &HashMap<(&usize, &usize), usize>, from: usize, to: usize) -> usize {
+  match distances.get(&(&from, &to)) {
+    Some(distance) => *distance,
+    None => panic!("No distance between {from} and {to}!"),
+  }
+}
+
+#[inline]
+fn remove_position_from_vec(mut positions: Vec<usize>, needle: &usize) -> Vec<usize> {
+  positions.retain(|elt| elt != needle);
+  return positions;
+}
+
+fn best_path_v1(
+  distances: &HashMap<(&usize, &usize), usize>,
+  position: usize,
+  positions_left: Vec<usize>,
+  path: usize,
+  mut best_path: usize,
+) -> usize {
+  if path > best_path {
+    return path;
+  }
+  if positions_left.is_empty() {
+    return path;
+  }
+  for next_position in positions_left.iter() {
+    let next_positions_left = remove_position_from_vec(positions_left.clone(), next_position);
+    let next_path = path + get_distance(&distances, position, *next_position);
+    let next_distance = best_path_v1(
+      &distances,
+      *next_position,
+      next_positions_left,
+      next_path,
+      best_path,
+    );
+    best_path = std::cmp::min(best_path, next_distance);
+  }
+
+  best_path
+}
+
+pub fn day_24_v1(input: impl Into<String>) -> usize {
+  let labyrinth = Labyrinth::new(&input.into());
+  let numbers: Vec<_> = (0..labyrinth.numbers.len()).collect();
+  let mut distances = HashMap::new();
+  let combos: Vec<_> = numbers.iter().combinations(2).collect();
+  combos.iter().for_each(|pair| {
+    let starter = labyrinth.numbers[*pair[0]];
+    let ending = labyrinth.numbers[*pair[1]];
+    let mut bfs = BreadthFirstSearch::new(starter, |position| labyrinth.next_moves(position));
+    let distance = bfs.shortest_path_to(ending);
+    distances.insert((pair[0], pair[1]), distance);
+    distances.insert((pair[1], pair[0]), distance);
+  });
+
+  best_path_v1(
+    &distances,
+    0,
+    (1..labyrinth.numbers.len()).collect(),
+    0,
+    usize::MAX,
+  )
+}
+
+fn best_path_v2(
+  distances: &HashMap<(&usize, &usize), usize>,
+  position: usize,
+  positions_left: Vec<usize>,
+  path: usize,
+  mut best_path: usize,
+) -> usize {
+  if path > best_path {
+    return path;
+  }
+  if positions_left.is_empty() {
+    return path + get_distance(&distances, position, 0);
+  }
+  for next_position in positions_left.iter() {
+    let next_positions_left = remove_position_from_vec(positions_left.clone(), next_position);
+    let next_path = path + get_distance(&distances, position, *next_position);
+    let next_distance = best_path_v2(
+      &distances,
+      *next_position,
+      next_positions_left,
+      next_path,
+      best_path,
+    );
+    best_path = std::cmp::min(best_path, next_distance);
+  }
+
+  best_path
+}
+
+pub fn day_24_v2(input: impl Into<String>) -> usize {
+  let labyrinth = Labyrinth::new(&input.into());
+  let numbers: Vec<_> = (0..labyrinth.numbers.len()).collect();
+  let mut distances = HashMap::new();
+  let combos: Vec<_> = numbers.iter().combinations(2).collect();
+  combos.iter().for_each(|pair| {
+    let starter = labyrinth.numbers[*pair[0]];
+    let ending = labyrinth.numbers[*pair[1]];
+    let mut bfs = BreadthFirstSearch::new(starter, |position| labyrinth.next_moves(position));
+    let distance = bfs.shortest_path_to(ending);
+    distances.insert((pair[0], pair[1]), distance);
+    distances.insert((pair[1], pair[0]), distance);
+  });
+
+  best_path_v2(
+    &distances,
+    0,
+    (1..labyrinth.numbers.len()).collect(),
+    0,
+    usize::MAX,
+  )
+}
+
+solvable!(day_24, day_24_v1, day_24_v2, usize);
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[test]
+  fn works_with_samples_v1() {
+    let sample = "###########\n\
+      #0.1.....2#\n\
+      #.#######.#\n\
+      #4.......3#\n\
+      ###########";
+    assert_eq!(day_24_v1(sample), 14);
+  }
+}