Day 6

src/bin/06.rs

@@ -0,0 +1,38 @@
+use std::collections::VecDeque;
+
+type School = VecDeque<u64>;
+
+fn main() {
+    let mut fish = input();
+    for _ in 0..80 {
+        step(&mut fish);
+    }
+    println!("First solution: {}", sum(&fish));
+
+    let mut fish = input();
+    for _ in 0..256 {
+        step(&mut fish);
+    }
+    println!("Second solution: {}", sum(&fish));
+}
+
+fn step(fish: &mut School) {
+    let front = fish.pop_front().unwrap();
+    fish.push_back(front);
+    fish[6] += front;
+}
+
+fn sum(fish: &School) -> u64 {
+    fish.iter().sum()
+}
+
+fn input() -> School {
+    let init: School = vec![0; 9].into();
+    include_str!("../../input/06.txt")
+        .split(',')
+        .map(|n| n.parse().unwrap())
+        .fold(init, |mut acc, n| {
+            acc[n] += 1;
+            acc
+        })
+}