From 02566256087a702061d0395a5ca70666908ef671 Mon Sep 17 00:00:00 2001
From: kageru <kageru@encode.moe>
Date: Mon, 6 Dec 2021 11:01:23 +0100
Subject: [PATCH] Add day 6 part 1

---
 2021/inputs/day06     |  1 +
 2021/src/bin/day06.rs | 54 +++++++++++++++++++++++++++++++++++++++++++
 2021/src/common.rs    |  8 +++++--
 3 files changed, 61 insertions(+), 2 deletions(-)
 create mode 100644 2021/inputs/day06
 create mode 100644 2021/src/bin/day06.rs

diff --git a/2021/inputs/day06 b/2021/inputs/day06
new file mode 100644
index 0000000..52d28e3
--- /dev/null
+++ b/2021/inputs/day06
@@ -0,0 +1 @@
+3,5,3,5,1,3,1,1,5,5,1,1,1,2,2,2,3,1,1,5,1,1,5,5,3,2,2,5,4,4,1,5,1,4,4,5,2,4,1,1,5,3,1,1,4,1,1,1,1,4,1,1,1,1,2,1,1,4,1,1,1,2,3,5,5,1,1,3,1,4,1,3,4,5,1,4,5,1,1,4,1,3,1,5,1,2,1,1,2,1,4,1,1,1,4,4,3,1,1,1,1,1,4,1,4,5,2,1,4,5,4,1,1,1,2,2,1,4,4,1,1,4,1,1,1,2,3,4,2,4,1,1,5,4,2,1,5,1,1,5,1,2,1,1,1,5,5,2,1,4,3,1,2,2,4,1,2,1,1,5,1,3,2,4,3,1,4,3,1,2,1,1,1,1,1,4,3,3,1,3,1,1,5,1,1,1,1,3,3,1,3,5,1,5,5,2,1,2,1,4,2,3,4,1,4,2,4,2,5,3,4,3,5,1,2,1,1,4,1,3,5,1,4,1,2,4,3,1,5,1,1,2,2,4,2,3,1,1,1,5,2,1,4,1,1,1,4,1,3,3,2,4,1,4,2,5,1,5,2,1,4,1,3,1,2,5,5,4,1,2,3,3,2,2,1,3,3,1,4,4,1,1,4,1,1,5,1,2,4,2,1,4,1,1,4,3,5,1,2,1
diff --git a/2021/src/bin/day06.rs b/2021/src/bin/day06.rs
new file mode 100644
index 0000000..3abbdc6
--- /dev/null
+++ b/2021/src/bin/day06.rs
@@ -0,0 +1,54 @@
+#![feature(test)]
+extern crate test;
+use aoc2021::common::*;
+use std::iter;
+
+const DAY: usize = 6;
+const DAYS_PER_CHILD: usize = 6;
+const DAYS_UNTIL_FERTILE: usize = 2;
+type Parsed = Vec<usize>;
+
+fn parse_input(raw: &str) -> Parsed {
+    parse_nums_comma(raw)
+}
+
+fn part1(parsed: &Parsed, generations: usize) -> usize {
+    iter::successors(Some(parsed.to_owned()), |fish| {
+        let fish = fish
+            .into_iter()
+            .flat_map(|n| match n {
+                0 => vec![DAYS_PER_CHILD, DAYS_PER_CHILD + DAYS_UNTIL_FERTILE],
+                &n => vec![n - 1],
+            })
+            .collect();
+        Some(fish)
+    })
+    .take(generations + 1)
+    .last()
+    .unwrap()
+    .len()
+}
+
+fn part2(parsed: &Parsed) -> usize {
+    unimplemented!()
+}
+
+fn main() {
+    let input = parse_input(&read_file(DAY));
+    println!("Part 1: {}", part1(&input, 80));
+    println!("Part 2: {}", part2(&input));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use aoc2021::*;
+
+    const TEST_INPUT: &str = "3,4,3,1,2";
+
+    test!(part1(80) == 5934);
+    test!(part2() == 0);
+    bench!(part1(80) == 364461);
+    bench!(part2() == 0);
+    bench_input!(Vec::len => 0);
+}
diff --git a/2021/src/common.rs b/2021/src/common.rs
index 2a9437b..2c55005 100644
--- a/2021/src/common.rs
+++ b/2021/src/common.rs
@@ -6,10 +6,14 @@ pub fn read_file(day: usize) -> String {
 
 #[inline]
 pub fn parse_nums(l: &str) -> Vec<usize> {
-    l.lines().filter_map(|n| n.parse().ok()).collect()
+    l.lines().map(parse_num).collect()
 }
 
 #[inline]
 pub fn parse_nums_comma(l: &str) -> Vec<usize> {
-    l.split(',').filter_map(|n| n.parse().ok()).collect()
+    l.split(',').map(parse_num).collect()
+}
+
+fn parse_num(s: &str) -> usize {
+    s.trim().parse().unwrap_or_else(|e| panic!("Invalid number {s}: {e:?}"))
 }