From 06c8b775fa536f6a2142cb39c47594208b9ad0aa Mon Sep 17 00:00:00 2001
From: kageru <kageru@encode.moe>
Date: Sun, 12 Dec 2021 12:41:23 +0100
Subject: [PATCH] Add day 12 part 1

---
 2021/inputs/day12     |  24 ++++++++
 2021/src/bin/day12.rs | 124 ++++++++++++++++++++++++++++++++++++++++++
 2021/src/teststuff.rs |   9 +++
 3 files changed, 157 insertions(+)
 create mode 100644 2021/inputs/day12
 create mode 100644 2021/src/bin/day12.rs

diff --git a/2021/inputs/day12 b/2021/inputs/day12
new file mode 100644
index 0000000..fbb547b
--- /dev/null
+++ b/2021/inputs/day12
@@ -0,0 +1,24 @@
+yb-start
+de-vd
+rj-yb
+rj-VP
+OC-de
+MU-de
+end-DN
+vd-end
+WK-vd
+rj-de
+DN-vd
+start-VP
+DN-yb
+vd-MU
+DN-rj
+de-VP
+yb-OC
+start-rj
+oa-MU
+yb-de
+oa-VP
+jv-MU
+yb-MU
+end-OC
diff --git a/2021/src/bin/day12.rs b/2021/src/bin/day12.rs
new file mode 100644
index 0000000..84c58a5
--- /dev/null
+++ b/2021/src/bin/day12.rs
@@ -0,0 +1,124 @@
+#![feature(test)]
+extern crate test;
+use std::collections::{HashMap, HashSet};
+
+use aoc2021::common::*;
+use itertools::Itertools;
+
+const DAY: usize = 12;
+type Parsed<'a> = HashMap<Node<'a>, Vec<Node<'a>>>;
+
+const EMPTY: Vec<Node<'_>> = Vec::new();
+
+#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
+enum Node<'a> {
+    Start,
+    End,
+    Small(&'a str),
+    Big(&'a str),
+}
+
+impl<'a> From<&'a str> for Node<'a> {
+    fn from(s: &'a str) -> Self {
+        match s {
+            "start" => Node::Start,
+            "end" => Node::End,
+            cave if cave.chars().all(|c| c.is_ascii_uppercase()) => Node::Big(cave),
+            cave if cave.chars().all(|c| c.is_ascii_lowercase()) => Node::Small(cave),
+            _ => unreachable!(),
+        }
+    }
+}
+
+fn parse_input(raw: &str) -> Parsed {
+    raw.lines()
+        .map(|l| l.split_once('-').unwrap())
+        .map(|(from, to)| (Node::from(from), Node::from(to)))
+        .flat_map(|(a, b)| [(a, b), (b, a)]) // connections always go both ways
+        .into_group_map()
+}
+
+fn part1(parsed: &Parsed) -> usize {
+    possible_paths(parsed, &Node::Start, HashSet::new())
+}
+
+fn possible_paths<'a>(map: &'a Parsed, position: &'a Node<'a>, mut visited: HashSet<&'a Node<'a>>) -> usize {
+    if position == &Node::End {
+        return 1;
+    }
+    if matches!(position, &Node::Small(_)) {
+        visited.insert(position);
+    }
+    map.get(position)
+        .unwrap()
+        .iter()
+        .filter(|&p| p != &Node::Start)
+        .filter(|p| !visited.contains(p))
+        .map(|p| possible_paths(map, p, visited.clone()))
+        .sum()
+}
+
+fn part2(parsed: &Parsed) -> usize {
+    unimplemented!()
+}
+
+fn main() {
+    let raw = read_file(DAY);
+    let input = parse_input(&raw);
+    println!("Part 1: {}", part1(&input));
+    println!("Part 2: {}", part2(&input));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use aoc2021::*;
+
+    const TEST_INPUT: &str = "start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end";
+
+    const TEST_INPUT_2: &str = "dc-end
+HN-start
+start-kj
+dc-start
+dc-HN
+LN-dc
+HN-end
+kj-sa
+kj-HN
+kj-dc";
+
+    const TEST_INPUT_3: &str = "fs-end
+he-DX
+fs-he
+start-DX
+pj-DX
+end-zg
+zg-sl
+zg-pj
+pj-he
+RW-he
+fs-DX
+pj-RW
+zg-RW
+start-pj
+he-WI
+zg-he
+pj-fs
+start-RW";
+
+    test!(part1() == 10);
+    test!(with _2: part1() == 19);
+    test!(with _3: part1() == 226);
+    test!(part2() == 36);
+    test!(with _2: part2() == 103);
+    test!(with _3: part2() == 3509);
+    bench!(part1() == 4411);
+    bench!(part2() == 0);
+    bench_input!(HashMap::len => 13);
+}
diff --git a/2021/src/teststuff.rs b/2021/src/teststuff.rs
index f4f0814..6e572c9 100644
--- a/2021/src/teststuff.rs
+++ b/2021/src/teststuff.rs
@@ -34,4 +34,13 @@ macro_rules! test {
             }
         }
     };
+    (with $input: ident: $part: ident $(<$gen: literal>)?  ($($param: expr),*) == $expected:expr) => {
+        paste::paste! {
+            #[test]
+            fn [<$part $($gen)? _$input:lower _test>]() {
+                let input = parse_input([<TEST_INPUT $input>]);
+                assert_eq!($part $(::<$gen>)? (&input$(, $param)*), $expected);
+            }
+        }
+    };
 }