Day 11: Plutonian Pebbles

README.md

@@ -15,4 +15,4 @@ Development occurs in language-specific directories:
 |[Day8.hs](hs/src/Day8.hs)|[Day8.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day8.kt)|[day8.py](py/aoc2024/day8.py)|[day8.rs](rs/src/day8.rs)|
 |[Day9.hs](hs/src/Day9.hs)|[Day9.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day9.kt)|[day9.py](py/aoc2024/day9.py)|[day9.rs](rs/src/day9.rs)|
 |[Day10.hs](hs/src/Day10.hs)|[Day10.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day10.kt)|[day10.py](py/aoc2024/day10.py)|[day10.rs](rs/src/day10.rs)|
-|[Day11.hs](hs/src/Day11.hs)|[Day11.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day11.kt)|[day11.py](py/aoc2024/day11.py)||
+|[Day11.hs](hs/src/Day11.hs)|[Day11.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day11.kt)|[day11.py](py/aoc2024/day11.py)|[day11.rs](rs/src/day11.rs)|

rs/benches/criterion.rs

@@ -1,4 +1,4 @@
-use aoc2024::{day1, day10, day2, day3, day4, day5, day6, day7, day8, day9};
+use aoc2024::{day1, day10, day11, day2, day3, day4, day5, day6, day7, day8, day9};
 use criterion::{black_box, Criterion};
 use std::env;
 use std::fs;
@@ -74,6 +74,12 @@ fn aoc2024_bench(c: &mut Criterion) -> io::Result<()> {
     g.bench_function("part 2", |b| b.iter(|| day10::part2(black_box(&data))));
     g.finish();
 
+    let data = get_day_input(11)?;
+    let mut g = c.benchmark_group("day 11");
+    g.bench_function("part 1", |b| b.iter(|| day11::part1(black_box(&data))));
+    g.bench_function("part 2", |b| b.iter(|| day11::part2(black_box(&data))));
+    g.finish();
+
     Ok(())
 }
 

rs/src/day11.rs

@@ -0,0 +1,74 @@
+use std::collections::BTreeMap;
+use std::num::ParseIntError;
+
+pub fn part1(data: &str) -> Result<u64, ParseIntError> {
+    solve(data, 25)
+}
+
+pub fn part2(data: &str) -> Result<u64, ParseIntError> {
+    solve(data, 75)
+}
+
+fn solve(data: &str, n: usize) -> Result<u64, ParseIntError> {
+    Ok((0..n)
+        .fold(
+            {
+                let mut counts = BTreeMap::new();
+                for word in data.split_ascii_whitespace() {
+                    counts
+                        .entry(word.parse::<u64>()?)
+                        .and_modify(|e| *e += 1)
+                        .or_insert(1u64);
+                }
+                counts
+            },
+            |counts, _| {
+                let mut next = BTreeMap::new();
+                for (num, count) in counts {
+                    if num == 0 {
+                        next.entry(1).and_modify(|e| *e += count).or_insert(count);
+                    } else {
+                        let length = num.ilog10() + 1;
+                        if length % 2 == 0 {
+                            let divisor = 10u64.pow(length / 2);
+                            next.entry(num / divisor)
+                                .and_modify(|e| *e += count)
+                                .or_insert(count);
+                            next.entry(num % divisor)
+                                .and_modify(|e| *e += count)
+                                .or_insert(count);
+                        } else {
+                            next.entry(2024 * num)
+                                .and_modify(|e| *e += count)
+                                .or_insert(count);
+                        }
+                    }
+                }
+                next
+            },
+        )
+        .into_values()
+        .sum())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use indoc::indoc;
+    use pretty_assertions::assert_eq;
+
+    static EXAMPLE_1: &str = indoc! {"
+        0 1 10 99 999
+    "};
+
+    static EXAMPLE_2: &str = indoc! {"
+        125 17
+    "};
+
+    #[test]
+    fn part1_examples() {
+        assert_eq!(Ok(7), solve(EXAMPLE_1, 1));
+        assert_eq!(Ok(22), solve(EXAMPLE_2, 6));
+        assert_eq!(Ok(55312), solve(EXAMPLE_2, 25));
+    }
+}

rs/src/lib.rs

@@ -1,5 +1,6 @@
 pub mod day1;
 pub mod day10;
+pub mod day11;
 pub mod day2;
 pub mod day3;
 pub mod day4;

rs/src/main.rs

@@ -1,5 +1,5 @@
 use anyhow::anyhow;
-use aoc2024::{day1, day10, day2, day3, day4, day5, day6, day7, day8, day9};
+use aoc2024::{day1, day10, day11, day2, day3, day4, day5, day6, day7, day8, day9};
 use std::collections::HashSet;
 use std::env;
 use std::fs;
@@ -97,5 +97,13 @@ fn main() -> anyhow::Result<()> {
         println!();
     }
 
+    if args.is_empty() || args.contains("11") {
+        println!("Day 11");
+        let data = get_day_input(11)?;
+        println!("{:?}", day11::part1(&data)?);
+        println!("{:?}", day11::part2(&data)?);
+        println!();
+    }
+
     Ok(())
 }