3 files changed, 97 insertions(+), 0 deletions(-)

A input/day11/example
A src/day11/mod.rs
M src/main.rs

@@ 0,0 1,1 @@
+125 17

@@ 0,0 1,88 @@
+use std::{
+    collections::HashMap,
+    fs::File,
+    io::{BufRead, BufReader},
+    path::Path,
+};
+
+pub fn solve(input: &Path) -> anyhow::Result<()> {
+    println!("part one: {}", part_one(input)?);
+    println!("part two: {}", part_two(input)?);
+
+    Ok(())
+}
+
+fn part_one(input: &Path) -> anyhow::Result<usize> {
+    let mut reader = BufReader::new(File::open(input)?);
+
+    let mut input_str = String::new();
+    let _ = reader.read_line(&mut input_str)?;
+    let mut stones: Vec<Vec<usize>> = input_str
+        .split_whitespace()
+        .map(|c| -> Vec<usize> { vec![c.to_string().parse().unwrap()] })
+        .collect();
+
+    for _ in 0..25 {
+        for stone in &mut stones {
+            if stone[0] == 0 {
+                stone[0] = 1;
+                continue;
+            }
+            let stone_str = stone[0].to_string();
+            if stone_str.len() % 2 == 0 {
+                let (right, left) = stone_str.split_at(stone_str.len() / 2);
+                *stone = vec![right.parse()?, left.parse()?];
+            } else {
+                stone[0] *= 2024;
+            }
+        }
+        stones = stones
+            .iter()
+            .flatten()
+            .map(|stone| -> Vec<usize> { vec![*stone] })
+            .collect();
+    }
+
+    Ok(stones.iter().flatten().count())
+}
+
+fn part_two(input: &Path) -> anyhow::Result<usize> {
+    let mut reader = BufReader::new(File::open(input)?);
+
+    let mut input_str = String::new();
+    let _ = reader.read_line(&mut input_str)?;
+    let input_stones: Vec<usize> = input_str
+        .split_whitespace()
+        .map(|c| -> usize { c.to_string().parse().unwrap() })
+        .collect();
+    let mut stones: HashMap<usize, usize> = HashMap::new();
+    for stone in input_stones {
+        if let Some(amount) = stones.get_mut(&stone) {
+            *amount += 1;
+        } else {
+            stones.insert(stone, 1);
+        }
+    }
+    for _ in 0..75 {
+        for (stone, amount) in &stones.clone() {
+            *stones.entry(*stone).or_insert(0) -= amount;
+            if *stone == 0 {
+                *stones.entry(1).or_insert(0) += amount;
+                continue;
+            }
+            let stone_str = stone.to_string();
+            if stone_str.len() % 2 == 0 {
+                let (right, left) = stone_str.split_at(stone_str.len() / 2);
+                let right = right.parse()?;
+                let left = left.parse()?;
+                *stones.entry(right).or_insert(0) += amount;
+                *stones.entry(left).or_insert(0) += amount;
+            } else {
+                let new = stone * 2024;
+                *stones.entry(new).or_insert(0) += amount;
+            }
+        }
+    }
+
+    Ok(stones.values().sum())
+}

@@ 4,6 4,7 @@ use clap::{Parser, Subcommand};
 
 mod day1;
 mod day10;
+mod day11;
 mod day2;
 mod day3;
 mod day4;


@@ 61,6 62,10 @@ enum DayArgs {
         #[arg(short)]
         input: PathBuf,
     },
+    Day11 {
+        #[arg(short)]
+        input: PathBuf,
+    },
 }
 
 fn main() -> anyhow::Result<()> {


@@ 97,6 102,9 @@ fn main() -> anyhow::Result<()> {
         DayArgs::Day10 { input } => {
             day10::solve(&input)?;
         }
+        DayArgs::Day11 { input } => {
+            day11::solve(&input)?;
+        }
     }
 
     Ok(())