feat: impl day 7

1 files changed, 186 insertions, 0 deletions

diff --git a/src/day_07.rs b/src/day_07.rs
new file mode 100644
index 0000000..e688d16
--- /dev/null
+++ b/src/day_07.rs
@@ -0,0 +1,186 @@
+use std::{cmp::Reverse, collections::BTreeMap, str::FromStr};
+
+use anyhow::Context;
+
+use crate::{Problem, Solution};
+
+pub struct Day07;
+
+impl Problem for Day07 {
+    const DAY: u8 = 7;
+
+    const INPUT: &'static str = include_str!("../input/day_07.txt");
+}
+
+impl Solution for Day07 {
+    type Answer1 = usize;
+
+    type Answer2 = usize;
+
+    fn part_1(input: &str) -> anyhow::Result<Self::Answer1> {
+        let hand_bets = input
+            .lines()
+            .map(|s| {
+                s.trim()
+                    .split_once(' ')
+                    .with_context(|| format!("Invalid had format: {s}"))
+                    .and_then(|(hand, bet)| anyhow::Ok((Reverse(hand.parse()?), bet.parse()?)))
+            })
+            .try_collect::<BTreeMap<Reverse<Hand<false>>, usize>>()?;
+
+        Ok(hand_bets
+            .into_values()
+            .enumerate()
+            .map(|(i, bid)| bid * (i + 1))
+            .sum())
+    }
+
+    fn part_2(input: &str) -> anyhow::Result<Self::Answer2> {
+        let hand_bets = input
+            .lines()
+            .map(|s| {
+                s.trim()
+                    .split_once(' ')
+                    .with_context(|| format!("Invalid had format: {s}"))
+                    .and_then(|(hand, bet)| anyhow::Ok((Reverse(hand.parse()?), bet.parse()?)))
+            })
+            .try_collect::<BTreeMap<Reverse<Hand<true>>, usize>>()?;
+
+        Ok(hand_bets
+            .into_values()
+            .enumerate()
+            .map(|(i, bid)| bid * (i + 1))
+            .sum())
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+enum Hand<const WILD: bool> {
+    FiveOfAKind([Card<WILD>; 5]),
+    FourOfAKind([Card<WILD>; 5]),
+    FullHouse([Card<WILD>; 5]),
+    ThreeOfAKind([Card<WILD>; 5]),
+    TwoPair([Card<WILD>; 5]),
+    OnePair([Card<WILD>; 5]),
+    HighCard([Card<WILD>; 5]),
+}
+
+impl<const WILD: bool> Hand<WILD> {
+    fn count_types(mut cards: [Card<WILD>; 5]) -> (Vec<usize>, usize) {
+        cards.sort();
+
+        cards
+            .array_windows()
+            .rev()
+            .fold((Vec::from([1]), 0), |(mut acc, mut wilds), arr| {
+                match arr {
+                    [Card::Joker, Card::Joker] if wilds == 0 => wilds += 1,
+                    [_, Card::Joker] => wilds += 1,
+                    [p, n] if p == n => *acc.last_mut().unwrap() += 1,
+                    _ => acc.push(1),
+                }
+
+                (acc, wilds)
+            })
+    }
+}
+
+impl<const WILD: bool> From<[Card<WILD>; 5]> for Hand<WILD> {
+    fn from(cards: [Card<WILD>; 5]) -> Self {
+        let (mut counts, wilds) = Hand::count_types(cards);
+        counts.sort();
+
+        let n = counts.pop().unwrap();
+        let has_2 = counts.pop().is_some_and(|m| m == 2);
+
+        match (n + wilds).min(5) {
+            5 => Self::FiveOfAKind(cards),
+            4 => Self::FourOfAKind(cards),
+            3 if has_2 => Self::FullHouse(cards),
+            3 => Self::ThreeOfAKind(cards),
+            2 if has_2 => Self::TwoPair(cards),
+            2 => Self::OnePair(cards),
+            _ => Self::HighCard(cards),
+        }
+    }
+}
+impl<const WILD: bool> FromStr for Hand<WILD> {
+    type Err = anyhow::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let cards: [Card<WILD>; 5] = s
+            .chars()
+            .map(Card::try_from)
+            .try_collect::<Vec<_>>()?
+            .try_into()
+            .map_err(|v| anyhow::format_err!("Incorrect number of cards: {v:?}"))?;
+
+        Ok(Self::from(cards))
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+enum Card<const WILD: bool> {
+    Ace,
+    King,
+    Queen,
+    Jack,
+    Ten,
+    Nine,
+    Eight,
+    Seven,
+    Six,
+    Five,
+    Four,
+    Three,
+    Two,
+    Joker,
+}
+
+impl<const WILD: bool> TryFrom<char> for Card<WILD> {
+    type Error = anyhow::Error;
+
+    fn try_from(value: char) -> Result<Self, Self::Error> {
+        Ok(match value {
+            'A' => Card::Ace,
+            'K' => Card::King,
+            'Q' => Card::Queen,
+            'J' if WILD => Card::Joker,
+            'J' => Card::Jack,
+            'T' => Card::Ten,
+            '9' => Card::Nine,
+            '8' => Card::Eight,
+            '7' => Card::Seven,
+            '6' => Card::Six,
+            '5' => Card::Five,
+            '4' => Card::Four,
+            '3' => Card::Three,
+            '2' => Card::Two,
+            c => anyhow::bail!("Failed to parse card value: {c}"),
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    const INPUT: &str = indoc::indoc! {"
+        32T3K 765
+        T55J5 684
+        KK677 28
+        KTJJT 220
+        QQQJA 483
+    "};
+
+    #[test]
+    fn test_part_1() -> anyhow::Result<()> {
+        Ok(assert_eq!(6440, Day07::part_1(INPUT)?))
+    }
+
+    #[test]
+    fn test_part_2() -> anyhow::Result<()> {
+        Ok(assert_eq!(5905, Day07::part_2(INPUT)?))
+    }
+}