From e6cf50fb4795f2cdf7342811cabd426f584c7e3a Mon Sep 17 00:00:00 2001
From: Andrew Coleman <penguincoder@gmail.com>
Date: Wed, 13 Dec 2023 13:47:53 -0500
Subject: [PATCH] day12 solution. gross.

---
 2023/src/day12.rs | 208 ++++++++++++++++++++++++++++++++++++++++++++++
 2023/src/lib.rs   |   1 +
 2 files changed, 209 insertions(+)
 create mode 100644 2023/src/day12.rs

diff --git a/2023/src/day12.rs b/2023/src/day12.rs
new file mode 100644
index 0000000..0276a2f
--- /dev/null
+++ b/2023/src/day12.rs
@@ -0,0 +1,208 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use std::collections::HashMap;
+use std::str::FromStr;
+
+type Cache = HashMap<(Vec<Condition>, Vec<usize>), usize>;
+
+#[derive(Copy, Clone, Eq, PartialEq, Hash)]
+enum Condition {
+    Unknown,
+    Functional,
+    Damaged,
+}
+
+impl FromStr for Condition {
+    type Err = String;
+    fn from_str(input: &str) -> Result<Condition, Self::Err> {
+        match input {
+            "?" => Ok(Condition::Unknown),
+            "." => Ok(Condition::Functional),
+            "#" => Ok(Condition::Damaged),
+            n @ _ => Err(format!("Unknown character '{}'", n)),
+        }
+    }
+}
+
+#[derive(Clone)]
+struct Spring {
+    list: Vec<Condition>,
+    groups: Vec<usize>,
+}
+
+#[aoc_generator(day12)]
+fn parse(input: &str) -> Vec<Spring> {
+    input
+        .lines()
+        .filter_map(|line| {
+            if !line.is_empty() {
+                let parts = line.split(" ").collect::<Vec<&str>>();
+                let list = parts[0]
+                    .split("")
+                    .filter_map(|e| {
+                        if e.is_empty() {
+                            None
+                        } else {
+                            Condition::from_str(e).ok()
+                        }
+                    })
+                    .collect();
+                let groups = parts[1]
+                    .split(",")
+                    .map(|e| e.parse::<usize>().unwrap())
+                    .collect();
+                Some(Spring { list, groups })
+            } else {
+                None
+            }
+        })
+        .collect()
+}
+
+fn calc_solutions(list: &Vec<Condition>, groups: &Vec<usize>, cache: &mut Cache) -> usize {
+    if list.is_empty() {
+        if groups.is_empty() {
+            return 1;
+        } else {
+            return 0;
+        }
+    }
+
+    match list[0] {
+        Condition::Functional => calc_solutions(&list[1..].to_vec(), groups, cache),
+        Condition::Damaged => calc_damaged_solutions(list, groups, cache),
+        Condition::Unknown => {
+            calc_solutions(&list[1..].to_vec(), groups, cache)
+                + calc_damaged_solutions(list, groups, cache)
+        }
+    }
+}
+
+fn calc_damaged_solutions(list: &Vec<Condition>, groups: &Vec<usize>, cache: &mut Cache) -> usize {
+    if let Some(&result) = cache.get(&(list.clone(), groups.clone())) {
+        return result;
+    }
+
+    if groups.is_empty() {
+        return 0;
+    }
+
+    if list.len() < groups[0] {
+        return 0;
+    }
+
+    for i in 0..groups[0] {
+        if list[i] == Condition::Functional {
+            return 0;
+        }
+    }
+
+    if list.len() == groups[0] {
+        if groups.len() == 1 {
+            return 1;
+        }
+        return 0;
+    }
+    if list[groups[0]] == Condition::Damaged {
+        return 0;
+    }
+    let result = calc_solutions(
+        &list[(groups[0] + 1)..].to_vec(),
+        &groups[1..].to_vec(),
+        cache,
+    );
+    cache.insert((list.clone(), groups.clone()), result);
+    result
+}
+
+#[aoc(day12, part1)]
+fn part1(input: &[Spring]) -> usize {
+    let mut result: usize = 0;
+    for src in input.iter() {
+        let mut cache: Cache = HashMap::new();
+        result += calc_solutions(&src.list, &src.groups, &mut cache);
+    }
+    result
+}
+
+#[aoc(day12, part2)]
+fn part2(input: &[Spring]) -> usize {
+    let mut result: usize = 0;
+    for src in input.iter() {
+        let mut l: Vec<Condition> = Vec::with_capacity(src.groups.len() * 5 + 5);
+        let mut g: Vec<usize> = Vec::with_capacity(src.list.len() * 5);
+        for index in 0..5 {
+            l.append(&mut src.list.clone());
+            if index < 4 {
+                l.push(Condition::Unknown);
+            }
+            g.append(&mut src.groups.clone());
+        }
+        let mut cache: Cache = HashMap::new();
+        let s = calc_solutions(&l, &g, &mut cache);
+        result += s;
+    }
+    result
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const SAMPLE_DATA: &'static str = r#"???.### 1,1,3
+.??..??...?##. 1,1,3
+?#?#?#?#?#?#?#? 1,3,1,6
+????.#...#... 4,1,1
+????.######..#####. 1,6,5
+?###???????? 3,2,1
+"#;
+
+    #[test]
+    fn sample_data_part1() {
+        let input = parse(&SAMPLE_DATA);
+        assert_eq!(part1(&input), 21);
+    }
+
+    #[test]
+    fn sample_data_3() {
+        let line1 = Spring {
+            list: vec![
+                Condition::Unknown,
+                Condition::Unknown,
+                Condition::Unknown,
+                Condition::Functional,
+                Condition::Damaged,
+                Condition::Damaged,
+                Condition::Damaged,
+            ],
+            groups: vec![1, 1, 3],
+        };
+        assert_eq!(part2(&[line1]), 1);
+
+        let line2 = Spring {
+            list: vec![
+                Condition::Functional,
+                Condition::Unknown,
+                Condition::Unknown,
+                Condition::Functional,
+                Condition::Functional,
+                Condition::Unknown,
+                Condition::Unknown,
+                Condition::Functional,
+                Condition::Functional,
+                Condition::Functional,
+                Condition::Unknown,
+                Condition::Damaged,
+                Condition::Damaged,
+                Condition::Functional,
+            ],
+            groups: vec![1, 1, 3],
+        };
+        assert_eq!(part2(&[line2]), 16384);
+    }
+
+    #[test]
+    fn sample_data_part2() {
+        let input = parse(&SAMPLE_DATA);
+        assert_eq!(part2(&input), 525152);
+    }
+}
diff --git a/2023/src/lib.rs b/2023/src/lib.rs
index a5b2fe6..047c882 100644
--- a/2023/src/lib.rs
+++ b/2023/src/lib.rs
@@ -11,5 +11,6 @@ mod day08;
 mod day09;
 mod day10;
 mod day11;
+mod day12;
 
 aoc_lib! { year = 2023 }