Day 17 puzzles

Cargo.toml

@@ -20,3 +20,5 @@ num = "0.4.1"
 petgraph = "0.6.4"
 ndarray = "0.15.6"
 cached = "0.46.1"
+strum = { version = "0.25", features = ["derive", "strum_macros"] }
+strum_macros = "0.25"

README.md

@@ -25,7 +25,7 @@
 | 14  | [src/solutions/day14.rs](src/solutions/day14.rs)         | ⭐️⭐️   |
 | 15  | [src/solutions/day15.rs](src/solutions/day15.rs)         | ⭐️⭐️   |
 | 16  | [src/solutions/day16.rs](src/solutions/day16.rs)         | ⭐️⭐️   |
-<!-- | 17  | [src/solutions/day17.rs](src/solutions/day17.rs)         | ⭐️⭐️   | -->
+| 17  | [src/solutions/day17.rs](src/solutions/day17.rs)         | ⭐️⭐️   |
 <!-- | 18  | [src/solutions/day18.rs](src/solutions/day18.rs)         | ⭐️⭐️   | -->
 <!-- | 19  | [src/solutions/day19.rs](src/solutions/day19.rs)         | ⭐️⭐️   | -->
 <!-- | 20  | [src/solutions/day20.rs](src/solutions/day20.rs)         | ⭐️⭐️   | -->
@@ -34,8 +34,12 @@
 <!-- | 23  | [src/solutions/day23.rs](src/solutions/day23.rs)         | ⭐️⭐️   | -->
 <!-- | 24  | [src/solutions/day24.rs](src/solutions/day24.rs)         | ⭐️⭐️   | -->
 
+## Help
+
 Used this Reddit post for Day 12 part 2: <https://www.reddit.com/r/adventofcode/comments/18hbbxe/2023_day_12python_stepbystep_tutorial_with_bonus/>
 
+I implemented the algorithm described in this Reddit [post](https://www.reddit.com/r/adventofcode/comments/18k9ne5/comment/kdqp7jx/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button) for Day 17 ([Python code](https://topaz.github.io/paste/#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))
+
 ## Setup
 
 ```bash

src/lib.rs

@@ -74,6 +74,10 @@ pub fn run_day(data_dir: &str, day: &u32) -> Result<(), Error> {
             solutions::day16::main(data_dir);
             Ok(())
         }
+        17 => {
+            solutions::day17::main(data_dir);
+            Ok(())
+        }
         // <-- INSERT NEW DAY HERE -->
         _ => Err(Error::DayNotImplemented(*day)),
     }

src/solutions/day17.rs

@@ -0,0 +1,145 @@
+use crate::data::load;
+use num::Complex;
+use std::cmp::Ordering;
+use std::collections::{BinaryHeap, HashMap, HashSet};
+use thiserror::Error;
+
+#[derive(Error, Debug, PartialEq, Eq)]
+pub enum PuzzleErr {
+    #[error("Integer parsing error.")]
+    ParseIntError(#[from] std::num::ParseIntError),
+}
+
+fn parse_grid(input: &str) -> Result<HashMap<Complex<i32>, i32>, PuzzleErr> {
+    let mut grid = HashMap::new();
+    for (i, r) in input.trim().lines().enumerate() {
+        for (j, c) in r.trim().chars().enumerate() {
+            grid.insert(
+                Complex::<i32>::new(i as i32, j as i32),
+                c.to_string().parse::<i32>()?,
+            );
+        }
+    }
+    Ok(grid)
+}
+
+#[derive(Copy, Clone, Eq, PartialEq)]
+struct State {
+    coord: Complex<i32>,
+    prev_dir: Complex<i32>,
+    score: i32,
+}
+
+impl Ord for State {
+    fn cmp(&self, other: &Self) -> Ordering {
+        other
+            .score
+            .cmp(&self.score)
+            .then_with(|| self.coord.re.cmp(&other.coord.re))
+            .then_with(|| self.coord.im.cmp(&other.coord.im))
+    }
+}
+
+impl PartialOrd for State {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+fn turns(d: Complex<i32>) -> Vec<Complex<i32>> {
+    Vec::from_iter([Complex { re: 0, im: 1 } / d, Complex { re: 0, im: -1 } / d])
+}
+
+fn shortest_path(
+    start: &Complex<i32>,
+    end: &Complex<i32>,
+    grid: &HashMap<Complex<i32>, i32>,
+    min_steps: i32,
+    max_steps: i32,
+) -> i32 {
+    let mut queue = BinaryHeap::<State>::from_iter([
+        State {
+            coord: *start,
+            prev_dir: Complex { re: 1, im: 0 },
+            score: 0,
+        },
+        State {
+            coord: *start,
+            prev_dir: Complex { re: 0, im: 1 },
+            score: 0,
+        },
+    ]);
+    let mut visited = HashSet::<(Complex<i32>, Complex<i32>)>::new();
+    while !queue.is_empty() {
+        let state = queue.pop().unwrap();
+        if &state.coord == end {
+            return state.score;
+        }
+        if visited.contains(&(state.coord, state.prev_dir)) {
+            continue;
+        }
+        visited.insert((state.coord, state.prev_dir));
+
+        for next_dir in turns(state.prev_dir) {
+            for i in min_steps..=max_steps {
+                if grid.contains_key(&(state.coord + (next_dir * i))) {
+                    let y: i32 = (1..=i)
+                        .map(|j| grid.get(&(state.coord + next_dir * j)).unwrap())
+                        .sum();
+                    let new_state = State {
+                        coord: state.coord + next_dir * i,
+                        prev_dir: next_dir,
+                        score: state.score + y,
+                    };
+                    queue.push(new_state);
+                }
+            }
+        }
+    }
+    unreachable!();
+}
+
+pub fn puzzle_1(input: &str) -> Result<i32, PuzzleErr> {
+    let grid = parse_grid(input)?;
+    let start = Complex { re: 0, im: 0 };
+    let end_re = grid.keys().map(|x| x.re).max().unwrap();
+    let end_im = grid.keys().map(|x| x.im).max().unwrap();
+    let end = Complex {
+        re: end_re,
+        im: end_im,
+    };
+    Ok(shortest_path(&start, &end, &grid, 1, 3))
+}
+
+pub fn puzzle_2(input: &str) -> Result<i32, PuzzleErr> {
+    let grid = parse_grid(input)?;
+    let start = Complex { re: 0, im: 0 };
+    let end_re = grid.keys().map(|x| x.re).max().unwrap();
+    let end_im = grid.keys().map(|x| x.im).max().unwrap();
+    let end = Complex {
+        re: end_re,
+        im: end_im,
+    };
+    Ok(shortest_path(&start, &end, &grid, 4, 10))
+}
+
+pub fn main(data_dir: &str) {
+    println!("Day 17: Clumsy Crucible");
+    let data = load(data_dir, 17, None);
+
+    // Puzzle 1.
+    let answer_1 = puzzle_1(&data);
+    match answer_1 {
+        Ok(x) => println!(" Puzzle 1: {}", x),
+        Err(e) => panic!("No solution to puzzle 1: {}.", e),
+    }
+    assert_eq!(answer_1, Ok(1076));
+
+    // Puzzle 2.
+    let answer_2 = puzzle_2(&data);
+    match answer_2 {
+        Ok(x) => println!(" Puzzle 2: {}", x),
+        Err(e) => panic!("No solution to puzzle 2: {}", e),
+    }
+    assert_eq!(answer_2, Ok(1219))
+}

src/solutions/mod.rs

@@ -14,3 +14,4 @@ pub mod day13;
 pub mod day14;
 pub mod day15;
 pub mod day16;
+pub mod day17;

tests/test_day17.rs

@@ -0,0 +1,43 @@
+use aoc_2023::solutions::day17::{puzzle_1, puzzle_2};
+
+const EXAMPLE_INPUT_1: &str = "
+2413432311323
+3215453535623
+3255245654254
+3446585845452
+4546657867536
+1438598798454
+4457876987766
+3637877979653
+4654967986887
+4564679986453
+1224686865563
+2546548887735
+4322674655533
+";
+
+#[test]
+fn puzzle_1_example_1() {
+    let _ = env_logger::try_init();
+    assert_eq!(puzzle_1(self::EXAMPLE_INPUT_1), Ok(102));
+}
+
+#[test]
+fn puzzle_2_example_1() {
+    let _ = env_logger::try_init();
+    assert_eq!(puzzle_2(self::EXAMPLE_INPUT_1), Ok(94));
+}
+
+const EXAMPLE_INPUT_2: &str = "
+111111111111
+999999999991
+999999999991
+999999999991
+999999999991
+";
+
+#[test]
+fn puzzle_2_example_2() {
+    let _ = env_logger::try_init();
+    assert_eq!(puzzle_2(self::EXAMPLE_INPUT_2), Ok(71));
+}