1 files changed, 153 insertions, 0 deletions
diff --git a/2023/day7/src/lib.rs b/2023/day7/src/lib.rs
new file mode 100644
index 0000000..02cd337
--- /dev/null
+++ b/2023/day7/src/lib.rs
@@ -0,0 +1,153 @@
+use std::{collections::HashMap, str::FromStr};
+
+#[derive(Debug, PartialEq, PartialOrd, Eq, Hash)]
+enum HandType {
+    Five,
+    Four,
+    Full,
+    Three,
+    Two,
+    One,
+    High,
+}
+
+#[derive(Debug)]
+struct Play {
+    hand: Vec<u32>,
+    bid: u32,
+    hand_type: HandType,
+}
+
+#[derive(Debug)]
+struct PlayError;
+
+impl FromStr for Play {
+    type Err = PlayError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if !s.contains(' ') {
+            return Err(PlayError);
+        }
+
+        let s: Vec<String> = s.split(' ').map(|x| x.to_string()).collect();
+        if s.len() != 2 {
+            return Err(PlayError);
+        }
+
+        let mut diffcards: HashMap<char, u32> = HashMap::new();
+        let hand = s[0].chars().collect::<Vec<char>>();
+
+        for ch in &hand {
+            if diffcards.contains_key(&ch) {
+                *(diffcards.get_mut(ch).unwrap()) += 1;
+            } else {
+                diffcards.insert(*ch, 1);
+            }
+        }
+
+        let card_points: HashMap<char, u32> = HashMap::from([
+            ('A', 13),
+            ('K', 12),
+            ('Q', 11),
+            ('J', 10),
+            ('T', 9),
+            ('9', 8),
+            ('8', 7),
+            ('7', 6),
+            ('6', 5),
+            ('5', 4),
+            ('4', 3),
+            ('3', 2),
+            ('2', 1),
+        ]);
+        let hand: Vec<_> = hand.iter().map(|x| *card_points.get(&x).unwrap()).collect();
+
+        let b: Vec<u32> = diffcards.clone().into_values().collect();
+        let max_labels: u32 = *b.iter().max().unwrap();
+
+        let hand_type: HandType = match diffcards.keys().len() {
+            1 => HandType::Five,
+            2 if max_labels == 4 => HandType::Four,
+            2 if max_labels == 3 => HandType::Full,
+            3 if max_labels == 3 => HandType::Three,
+            3 => HandType::Two,
+            4 => HandType::One,
+            5 => HandType::High,
+            _ => panic!("wtf is this?"),
+        };
+
+        Ok(Play {
+            hand,
+            bid: s[1].parse::<u32>().unwrap(),
+            hand_type,
+        })
+    }
+}
+
+pub fn part1(input: &str) -> u32 {
+    let mut res: u32 = 0;
+
+    let plays: Vec<_> = input
+        .trim_end()
+        .split('\n')
+        .map(|x| x.parse::<Play>().unwrap())
+        .collect();
+
+    let mut hs: HashMap<HandType, Vec<Play>> = HashMap::from([
+        (HandType::Five, vec![]),
+        (HandType::Four, vec![]),
+        (HandType::Full, vec![]),
+        (HandType::Three, vec![]),
+        (HandType::Two, vec![]),
+        (HandType::One, vec![]),
+        (HandType::High, vec![]),
+    ]);
+
+    for play in plays {
+        if let Some(p) = hs.get_mut(&play.hand_type) {
+            p.push(play);
+        }
+    }
+
+    let mut rank = 1;
+
+    for kind in [
+        HandType::High,
+        HandType::One,
+        HandType::Two,
+        HandType::Three,
+        HandType::Full,
+        HandType::Four,
+        HandType::Five,
+    ] {
+        hs.get_mut(&kind)
+            .unwrap()
+            .sort_by(|a, b| a.hand.partial_cmp(&b.hand).unwrap());
+
+        for h in hs.get(&kind).unwrap() {
+            res += rank * h.bid;
+            rank += 1;
+        }
+    }
+
+    res
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn example_part1() {
+        let input = include_str!("../example.txt");
+        let result = part1(input);
+        assert_eq!(result, 6440);
+    }
+
+    #[test]
+    fn input_part1() {
+        let input = include_str!("../input.txt");
+        let result = part1(input);
+        assert_eq!(result, 248179786);
+    }
+}