Day 11 solutions

Author: Cadiac

README.md

@@ -96,3 +96,4 @@ This should start the server at `localhost:8080`.
 ❄️ [Day 08](aoc-solver/src/y2024/day08.rs)
 ❄️ [Day 09](aoc-solver/src/y2024/day09.rs)
 ❄️ [Day 10](aoc-solver/src/y2024/day10.rs)
+❄️ [Day 11](aoc-solver/src/y2024/day11.rs)

aoc-solver/src/y2024/day11.rs

@@ -0,0 +1,95 @@
+use std::collections::HashMap;
+
+use crate::solution::{AocError, Solution};
+
+type Cache = HashMap<u64, HashMap<usize, usize>>;
+
+fn parse(input: &str) -> Result<Vec<u64>, AocError> {
+    input
+        .split_ascii_whitespace()
+        .map(|number| {
+            number
+                .parse::<u64>()
+                .map_err(|err| AocError::parse(number, err))
+        })
+        .collect()
+}
+
+fn split(stone: u64) -> Option<(u64, u64)> {
+    let digits = stone.ilog10() + 1;
+    if digits % 2 != 0 {
+        return None;
+    }
+
+    let divisor = 10u64.pow(digits / 2);
+    let left = stone / divisor;
+    let right = stone % divisor;
+
+    Some((left, right))
+}
+
+fn simulate(stone: u64, steps: usize, cache: &mut Cache) -> usize {
+    if steps == 0 {
+        return 1;
+    }
+
+    if let Some(&count) = cache.get(&stone).and_then(|counts| counts.get(&steps)) {
+        return count;
+    }
+
+    let count = if stone == 0 {
+        simulate(1, steps - 1, cache)
+    } else if let Some((left, right)) = split(stone) {
+        simulate(left, steps - 1, cache) + simulate(right, steps - 1, cache)
+    } else {
+        simulate(stone * 2024, steps - 1, cache)
+    };
+
+    cache.entry(stone).or_default().insert(steps, count);
+
+    count
+}
+
+pub struct Day11;
+impl Solution for Day11 {
+    type A = usize;
+    type B = usize;
+
+    fn default_input(&self) -> &'static str {
+        include_str!("../../../inputs/2024/day11.txt")
+    }
+
+    fn part_1(&self, input: &str) -> Result<usize, AocError> {
+        let stones = parse(input)?;
+        let mut cache = HashMap::new();
+
+        let count = stones
+            .into_iter()
+            .map(|stone| simulate(stone, 25, &mut cache))
+            .sum();
+
+        Ok(count)
+    }
+
+    fn part_2(&self, input: &str) -> Result<usize, AocError> {
+        let stones = parse(input)?;
+        let mut cache = HashMap::new();
+
+        let count = stones
+            .into_iter()
+            .map(|stone| simulate(stone, 75, &mut cache))
+            .sum();
+
+        Ok(count)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_solves_part1_example_1() {
+        assert_eq!(Day11.part_1("125 17"), Ok(55312));
+    }
+}

aoc-solver/src/y2024/mod.rs

@@ -10,7 +10,7 @@ pub mod day07;
 pub mod day08;
 pub mod day09;
 pub mod day10;
-// pub mod day11;
+pub mod day11;
 // pub mod day12;
 // pub mod day13;
 // pub mod day14;
@@ -26,7 +26,7 @@ pub mod day10;
 // pub mod day24;
 // pub mod day25;
 
-pub const MAX_DAYS: u8 = 10;
+pub const MAX_DAYS: u8 = 11;
 
 pub struct Y2024;
 
@@ -43,7 +43,7 @@ impl Solver for Y2024 {
             8 => day08::Day08.run(input, 8, 2024),
             9 => day09::Day09.run(input, 9, 2024),
             10 => day10::Day10.run(input, 10, 2024),
-            // 11 => day11::Day11.run(input, 11, 2024),
+            11 => day11::Day11.run(input, 11, 2024),
             // 12 => day12::Day12.run(input, 12, 2024),
             // 13 => day13::Day13.run(input, 13, 2024),
             // 14 => day14::Day14.run(input, 14, 2024),
@@ -85,7 +85,7 @@ impl Solver for Y2024 {
             8 => include_str!("./day08.rs"),
             9 => include_str!("./day09.rs"),
             10 => include_str!("./day10.rs"),
-            // 11 => include_str!("./day11.rs"),
+            11 => include_str!("./day11.rs"),
             // 12 => include_str!("./day12.rs"),
             // 13 => include_str!("./day13.rs"),
             // 14 => include_str!("./day14.rs"),

aoc-web/src/header.rs

@@ -29,6 +29,7 @@ pub fn header(props: &HeaderProps) -> Html {
                                     <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"}/>
+                                    <NavLink route={Route::Solution { year: 2024, day: 11 }} current={props.route.clone()} text={"11"}/>
                                 </>
                             }
                         },

inputs/2024/day11.txt

@@ -0,0 +1 @@
+2 54 992917 5270417 2514 28561 0 990