day 11

README.md

@@ -36,6 +36,7 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 8](./src/bin/08.rs) | `36.5µs` | `116.8µs` |
 | [Day 9](./src/bin/09.rs) | `80.1µs` | `258.4ms` |
 | [Day 10](./src/bin/10.rs) | `464.5µs` | `28.4µs` |
+| [Day 11](./src/bin/11.rs) | `179.0µs` | `9.2ms` |
 
-**Total: 294.35ms**
+**Total: 303.73ms**
 <!--- benchmarking table --->

data/examples/11.txt

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

src/bin/11.rs

@@ -0,0 +1,103 @@
+use std::collections::HashMap;
+
+advent_of_code::solution!(11);
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let mut lookup = HashMap::new();
+    let stones: u64 = input
+        .trim()
+        .split(" ")
+        .map(|num_str| {
+            let curr_stone = num_str.parse().unwrap();
+            blink(&mut lookup, curr_stone, 0)
+        })
+        .sum();
+    Some(stones)
+}
+
+#[derive(Debug, Eq, Hash, PartialEq, Clone, Copy)]
+struct LookupKey(u64, u8);
+
+fn blink(lookup: &mut HashMap<LookupKey, u64>, curr_stone: u64, curr_step: u8) -> u64 {
+    // Break case
+    if curr_step == 25 {
+        return 1;
+    }
+
+    // Check Lookup
+    if let Some(&cached) = lookup.get(&LookupKey(curr_stone, curr_step)) {
+        return cached;
+    };
+
+    let res = if curr_stone == 0 {
+        blink(lookup, 1, curr_step + 1)
+    } else if curr_stone.to_string().len() % 2 == 0 {
+        let num_str = curr_stone.to_string();
+        let (l, r) = num_str.split_at(num_str.len() / 2);
+        blink(lookup, l.parse::<u64>().unwrap(), curr_step + 1)
+            + blink(lookup, r.parse::<u64>().unwrap(), curr_step + 1)
+    } else {
+        blink(lookup, curr_stone * 2024, curr_step + 1)
+    };
+
+    lookup.insert(LookupKey(curr_stone, curr_step), res);
+
+    res
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let mut lookup = HashMap::new();
+    let stones: u64 = input
+        .trim()
+        .split(" ")
+        .map(|num_str| {
+            let curr_stone = num_str.parse().unwrap();
+            blink2(&mut lookup, curr_stone, 0)
+        })
+        .sum();
+    Some(stones)
+}
+
+fn blink2(lookup: &mut HashMap<LookupKey, u64>, curr_stone: u64, curr_step: u8) -> u64 {
+    // Break case
+    if curr_step == 75 {
+        return 1;
+    }
+
+    // Check Lookup
+    if let Some(&cached) = lookup.get(&LookupKey(curr_stone, curr_step)) {
+        return cached;
+    };
+
+    let res = if curr_stone == 0 {
+        blink2(lookup, 1, curr_step + 1)
+    } else if curr_stone.to_string().len() % 2 == 0 {
+        let num_str = curr_stone.to_string();
+        let (l, r) = num_str.split_at(num_str.len() / 2);
+        blink2(lookup, l.parse::<u64>().unwrap(), curr_step + 1)
+            + blink2(lookup, r.parse::<u64>().unwrap(), curr_step + 1)
+    } else {
+        blink2(lookup, curr_stone * 2024, curr_step + 1)
+    };
+
+    lookup.insert(LookupKey(curr_stone, curr_step), res);
+
+    res
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(55312));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, None);
+    }
+}