Day 10 solutions

Author: Cadiac

README.md

@@ -95,3 +95,4 @@ This should start the server at `localhost:8080`.
 ❄️ [Day 07](aoc-solver/src/y2024/day07.rs)
 ❄️ [Day 08](aoc-solver/src/y2024/day08.rs)
 ❄️ [Day 09](aoc-solver/src/y2024/day09.rs)
+❄️ [Day 10](aoc-solver/src/y2024/day10.rs)

aoc-solver/src/y2024/day10.rs

@@ -0,0 +1,159 @@
+use std::collections::HashMap;
+
+use itertools::Itertools;
+
+use crate::solution::{AocError, Solution};
+
+type Grid = Vec<Vec<u32>>;
+
+struct Search {
+    elevation: u32,
+    coords: (usize, usize),
+}
+
+const DIRECTIONS: [(isize, isize); 4] = [(0, -1), (1, 0), (0, 1), (-1, 0)];
+
+fn parse(input: &str) -> Result<Grid, AocError> {
+    let area = input
+        .trim()
+        .lines()
+        .map(|line| {
+            line.trim()
+                .chars()
+                .map(|c| {
+                    c.to_digit(10)
+                        .ok_or_else(|| AocError::parse(c.to_string(), "Unexpected character"))
+                })
+                .collect()
+        })
+        .try_collect()?;
+
+    Ok(area)
+}
+
+fn is_within_bounds(x: isize, y: isize, width: isize, height: isize) -> bool {
+    x >= 0 && y >= 0 && x < width && y < height
+}
+
+fn search_trails((x, y): (usize, usize), grid: &[Vec<u32>]) -> HashMap<(usize, usize), usize> {
+    let mut stack: Vec<Search> = Vec::new();
+
+    let width = grid[0].len() as isize;
+    let height = grid.len() as isize;
+
+    stack.push(Search {
+        elevation: grid[y][x],
+        coords: (x, y),
+    });
+
+    let mut trails: HashMap<(usize, usize), usize> = HashMap::new();
+
+    while let Some(Search { coords, elevation }) = stack.pop() {
+        if elevation == 9 {
+            *trails.entry(coords).or_insert(0) += 1;
+            continue;
+        }
+
+        for (dx, dy) in DIRECTIONS {
+            let next: (isize, isize) = (coords.0 as isize + dx, coords.1 as isize + dy);
+
+            if is_within_bounds(next.0, next.1, width, height) {
+                let next_elevation = grid[next.1 as usize][next.0 as usize];
+
+                if next_elevation.saturating_sub(elevation) != 1 {
+                    // Trail should always increase by a height of exactly 1 at each step
+                    continue;
+                }
+
+                stack.push(Search {
+                    elevation: next_elevation,
+                    coords: (next.0 as usize, next.1 as usize),
+                });
+            }
+        }
+    }
+
+    trails
+}
+
+pub struct Day10;
+impl Solution for Day10 {
+    type A = usize;
+    type B = usize;
+
+    fn default_input(&self) -> &'static str {
+        include_str!("../../../inputs/2024/day10.txt")
+    }
+
+    fn part_1(&self, input: &str) -> Result<usize, AocError> {
+        let grid = parse(input)?;
+        let mut score = 0;
+
+        for y in 0..grid.len() {
+            for x in 0..grid[y].len() {
+                if grid[y][x] == 0 {
+                    let peaks = search_trails((x, y), &grid);
+                    score += peaks.len()
+                }
+            }
+        }
+
+        Ok(score)
+    }
+
+    fn part_2(&self, input: &str) -> Result<usize, AocError> {
+        let grid = parse(input)?;
+        let mut score = 0;
+
+        for y in 0..grid.len() {
+            for x in 0..grid[y].len() {
+                if grid[y][x] == 0 {
+                    let peaks = search_trails((x, y), &grid);
+                    let trails: usize = peaks.values().sum();
+                    score += trails
+                }
+            }
+        }
+
+        Ok(score)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_solves_part1_example_1() {
+        assert_eq!(
+            Day10.part_1(
+                "89010123\n\
+                 78121874\n\
+                 87430965\n\
+                 96549874\n\
+                 45678903\n\
+                 32019012\n\
+                 01329801\n\
+                 10456732"
+            ),
+            Ok(36)
+        );
+    }
+
+    #[test]
+    fn it_solves_part1_example_2() {
+        assert_eq!(
+            Day10.part_2(
+                "89010123\n\
+                 78121874\n\
+                 87430965\n\
+                 96549874\n\
+                 45678903\n\
+                 32019012\n\
+                 01329801\n\
+                 10456732"
+            ),
+            Ok(81)
+        );
+    }
+}

aoc-solver/src/y2024/mod.rs

@@ -9,7 +9,7 @@ pub mod day06;
 pub mod day07;
 pub mod day08;
 pub mod day09;
-// pub mod day10;
+pub mod day10;
 // pub mod day11;
 // pub mod day12;
 // pub mod day13;
@@ -26,7 +26,7 @@ pub mod day09;
 // pub mod day24;
 // pub mod day25;
 
-pub const MAX_DAYS: u8 = 9;
+pub const MAX_DAYS: u8 = 10;
 
 pub struct Y2024;
 
@@ -42,7 +42,7 @@ impl Solver for Y2024 {
             7 => day07::Day07.run(input, 7, 2024),
             8 => day08::Day08.run(input, 8, 2024),
             9 => day09::Day09.run(input, 9, 2024),
-            // 10 => day10::Day10.run(input, 10, 2024),
+            10 => day10::Day10.run(input, 10, 2024),
             // 11 => day11::Day11.run(input, 11, 2024),
             // 12 => day12::Day12.run(input, 12, 2024),
             // 13 => day13::Day13.run(input, 13, 2024),

aoc-web/src/header.rs

@@ -28,6 +28,7 @@ pub fn header(props: &HeaderProps) -> Html {
                                     <NavLink route={Route::Solution { year: 2024, day: 7 }} current={props.route.clone()} text={"7"}/>
                                     <NavLink route={Route::Solution { year: 2024, day: 8 }} current={props.route.clone()} text={"8"}/>
                                     <NavLink route={Route::Solution { year: 2024, day: 9 }} current={props.route.clone()} text={"9"}/>
+                                    <NavLink route={Route::Solution { year: 2024, day: 10 }} current={props.route.clone()} text={"10"}/>
                                 </>
                             }
                         },

inputs/2024/day10.txt

@@ -0,0 +1,54 @@
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