day 11

src/day11.rs

@@ -0,0 +1,65 @@
+use std::{collections::HashMap, fs::read_to_string};
+
+pub fn day_main() {
+    let input = read_to_string("input/day11.txt").unwrap();
+    let input = input.trim();
+    println!(" part1: {}", part1(input));
+    println!(" part2: {}", part2(input));
+}
+
+type RiddleResult = usize;
+
+fn part1(input: &str) -> RiddleResult {
+    solve(input, 25)
+}
+
+fn solve(input: &str, blinks: i32) -> usize {
+    let mut stones: HashMap<String, usize> = input.split(" ").map(|v| (v.to_string(), 1)).collect();
+    let mut next = HashMap::new();
+    for _ in 0..blinks {
+        for (k, v) in stones {
+            if k.as_str() == "0" {
+                next.entry("1".to_string())
+                    .and_modify(|count| *count += v)
+                    .or_insert(v);
+            } else if k.len() % 2 == 0 {
+                let (a, b) = k.split_at(k.len() / 2);
+                next.entry(a.to_string())
+                    .and_modify(|count| *count += v)
+                    .or_insert(v);
+                let x = b.parse::<usize>().unwrap().to_string();
+                next.entry(x).and_modify(|count| *count += v).or_insert(v);
+            } else {
+                let d: usize = k.parse().unwrap();
+                let k_new = d * 2024;
+                next.entry(k_new.to_string())
+                    .and_modify(|count| *count += v)
+                    .or_insert(v);
+            }
+        }
+        stones = next;
+        next = HashMap::new();
+    }
+    stones.values().to_owned().sum()
+}
+
+fn part2(input: &str) -> RiddleResult {
+    solve(input, 75)
+}
+
+#[cfg(test)]
+mod test {
+    use super::{part1, part2};
+
+    const TEST_INPUT: &str = r"";
+
+    #[test]
+    fn test1() {
+        assert_eq!(part1("125 17"), 55312);
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(part2(TEST_INPUT), 0);
+    }
+}

src/lib.rs

@@ -8,5 +8,6 @@ pub mod day07;
 pub mod day08;
 pub mod day09;
 pub mod day10;
+pub mod day11;
 // PLACEHOLDER
 pub mod utils;

src/main.rs

@@ -15,6 +15,7 @@ fn main() {
         (8, day08::day_main),
         (9, day09::day_main),
         (10, day10::day_main),
+        (11, day11::day_main),
         // PLACEHOLDER
     ]);
     let day: Option<u8> = args().nth(1).and_then(|a| a.parse().ok());