Complete day 6

Cargo.lock

@@ -35,3 +35,11 @@ dependencies = [
  "anyhow",
  "common",
 ]
+
+[[package]]
+name = "day06"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "common",
+]

crates/day06/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "day06"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0"
+common = { path = "../common" }

crates/day06/src/input/input.txt

@@ -0,0 +1 @@
+3,1,4,2,1,1,1,1,1,1,1,4,1,4,1,2,1,1,2,1,3,4,5,1,1,4,1,3,3,1,1,1,1,3,3,1,3,3,1,5,5,1,1,3,1,1,2,1,1,1,3,1,4,3,2,1,4,3,3,1,1,1,1,5,1,4,1,1,1,4,1,4,4,1,5,1,1,4,5,1,1,2,1,1,1,4,1,2,1,1,1,1,1,1,5,1,3,1,1,4,4,1,1,5,1,2,1,1,1,1,5,1,3,1,1,1,2,2,1,4,1,3,1,4,1,2,1,1,1,1,1,3,2,5,4,4,1,3,2,1,4,1,3,1,1,1,2,1,1,5,1,2,1,1,1,2,1,4,3,1,1,1,4,1,1,1,1,1,2,2,1,1,5,1,1,3,1,2,5,5,1,4,1,1,1,1,1,2,1,1,1,1,4,5,1,1,1,1,1,1,1,1,1,3,4,4,1,1,4,1,3,4,1,5,4,2,5,1,2,1,1,1,1,1,1,4,3,2,1,1,3,2,5,2,5,5,1,3,1,2,1,1,1,1,1,1,1,1,1,3,1,1,1,3,1,4,1,4,2,1,3,4,1,1,1,2,3,1,1,1,4,1,2,5,1,2,1,5,1,1,2,1,2,1,1,1,1,4,3,4,1,5,5,4,1,1,5,2,1,3

crates/day06/src/input/test.txt

@@ -0,0 +1 @@
+3,4,3,1,2

crates/day06/src/main.rs

@@ -0,0 +1,88 @@
+use anyhow::Result;
+use common::instrument;
+use std::collections::HashMap;
+
+const INPUT: &str = include_str!("input/input.txt");
+
+fn simulate_day(fish: &mut Vec<u8>) {
+    for i in 0..fish.len() {
+        if fish[i] == 0 {
+            fish[i] = 6;
+            fish.push(8)
+        } else {
+            fish[i] -= 1;
+        }
+    }
+}
+
+fn simulate_day_with_map(fish_map: &HashMap<u8, u64>) -> HashMap<u8, u64> {
+    let mut new_map = HashMap::new();
+    for (day, count) in fish_map.into_iter() {
+        if *day == 0 {
+            let day8 = new_map.entry(8).or_insert(0);
+            *day8 += count;
+            let day6 = new_map.entry(6).or_insert(0);
+            *day6 += count;
+        } else {
+            let day_minus = new_map.entry(day - 1).or_insert(0);
+            *day_minus += count;
+        }
+    }
+    new_map
+}
+
+fn solve_part1(input: &str) -> Result<usize> {
+    let mut fish = input
+        .trim()
+        .split(',')
+        .map(|num| num.parse::<u8>())
+        .collect::<Result<Vec<_>, std::num::ParseIntError>>()?;
+
+    for _ in 0..80 {
+        simulate_day(&mut fish);
+    }
+
+    Ok(fish.len())
+}
+
+fn solve_part2(input: &str) -> Result<u64> {
+    let fish = input
+        .trim()
+        .split(',')
+        .map(|num| num.parse::<u8>())
+        .collect::<Result<Vec<_>, std::num::ParseIntError>>()?;
+
+    let mut fish_map: HashMap<u8, u64> = HashMap::new();
+
+    for f in fish.iter() {
+        let count = fish_map.entry(*f).or_insert(0);
+        *count += 1;
+    }
+
+    for _ in 0..256 {
+        fish_map = simulate_day_with_map(&fish_map);
+    }
+
+    Ok(fish_map.values().sum())
+}
+
+fn main() {
+    instrument!(solve_part1(INPUT).unwrap(), solve_part2(INPUT).unwrap());
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const TEST_INPUT: &str = include_str!("input/test.txt");
+
+    #[test]
+    fn solves_part1() {
+        assert_eq!(solve_part1(TEST_INPUT).unwrap(), 5934);
+    }
+
+    #[test]
+    fn solves_part2() {
+        assert_eq!(solve_part2(TEST_INPUT).unwrap(), 26984457539);
+    }
+}