day 11

src/main.rs

@@ -32,6 +32,7 @@ fn main() -> Result<()> {
         8 => AocDayEightSolution,
         9 => AocDayNineSolution,
         10 => AocDayTenSolution,
+        11 => AocDayElevenSolution,
     };
 
     Ok(())

src/solutions/day_11.rs

@@ -1,8 +1,58 @@
-use std::{fs::read_to_string, path::Path};
+use std::{collections::HashMap, fs::read_to_string, path::Path};
 
 use super::AocSolution;
 use crate::utils::Result;
 
+struct Stones {
+    stones: Vec<u64>,
+}
+
+impl Stones {
+    fn new(src: &str) -> Self {
+        Self {
+            stones: src
+                .split_whitespace()
+                .filter_map(|num| num.parse().ok())
+                .collect(),
+        }
+    }
+
+    fn blinks(&self, cnt: u8) -> u64 {
+        fn _inner(cache: &mut HashMap<(u64, u8), u64>, stone: u64, cnt: u8) -> u64 {
+            if cnt == 0 {
+                return 1;
+            }
+
+            if let Some(&val) = cache.get(&(stone, cnt)) {
+                return val;
+            }
+
+            let next = match stone {
+                0 => _inner(cache, 1, cnt - 1),
+                n => {
+                    let digits = n.ilog10() + 1;
+                    if digits % 2 == 0 {
+                        let pow = 10u64.pow(digits / 2);
+                        _inner(cache, stone / pow, cnt - 1) + _inner(cache, stone % pow, cnt - 1)
+                    } else {
+                        _inner(cache, stone * 2024, cnt - 1)
+                    }
+                }
+            };
+
+            cache.insert((stone, cnt), next);
+            next
+        }
+
+        let mut cache = HashMap::new();
+        self.stones
+            .iter()
+            .map(|&x| _inner(&mut cache, x, cnt))
+            .sum()
+    }
+}
+
+#[derive(Clone, Copy)]
 pub struct AocDayElevenSolution;
 
 impl AocSolution for AocDayElevenSolution {
@@ -11,15 +61,17 @@ impl AocSolution for AocDayElevenSolution {
     fn get_input(&self, path: Option<&Path>) -> Result<String> {
         Ok(match path {
             Some(p) => read_to_string(p)?,
-            None => read_to_string("./input/day_day_11.txt")?,
+            None => read_to_string("./input/day_11.txt")?,
         })
     }
 
     fn part_one(&self, input: &str) -> Result<Self::Output> {
-        todo!()
+        let stones = Stones::new(input);
+        Ok(stones.blinks(25))
     }
 
     fn part_two(&self, input: &str) -> Result<Self::Output> {
-        todo!()
+        let stones = Stones::new(input);
+        Ok(stones.blinks(75))
     }
 }

src/solutions/mod.rs

@@ -9,9 +9,8 @@ macro_rules! define_solution {
 }
 
 define_solution!(
-    day_1, day_2, day_3, day_4, day_5, day_6, day_7, day_8, day_9,
-    day_10,
-    // day_11,
+    day_1, day_2, day_3, day_4, day_5, day_6, day_7, day_8, day_9, day_10,
+    day_11,
     // day_12,
     // day_13,
     // day_14,