day 7 part 2

Cargo.lock

@@ -22,10 +22,17 @@ name = "aoc2023"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "counter",
  "fancy-regex",
  "regex",
 ]
 
+[[package]]
+name = "autocfg"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
+
 [[package]]
 name = "bit-set"
 version = "0.5.3"
@@ -41,6 +48,15 @@ version = "0.6.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "349f9b6a179ed607305526ca489b34ad0a41aed5f7980fa90eb03160b69598fb"
 
+[[package]]
+name = "counter"
+version = "0.5.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2d458e66999348f56fd3ffcfbb7f7951542075ca8359687c703de6500c1ddccd"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "fancy-regex"
 version = "0.12.0"
@@ -57,6 +73,15 @@ version = "2.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"
 
+[[package]]
+name = "num-traits"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39e3200413f237f41ab11ad6d161bc7239c84dcb631773ccd7de3dfe4b5c267c"
+dependencies = [
+ "autocfg",
+]
+
 [[package]]
 name = "regex"
 version = "1.10.2"

Cargo.toml

@@ -7,5 +7,6 @@ edition = "2021"
 
 [dependencies]
 anyhow = "1.0.75"
+counter = "0.5.7"
 fancy-regex = "0.12.0"
 regex = "1.10.2"

example.txt

@@ -1,2 +1,5 @@
-Time:      7  15   30
-Distance:  9  40  200
+32T3K 765
+T55J5 684
+KK677 28
+KTJJT 220
+QQQJA 483

src/main.rs

@@ -1,76 +1,119 @@
-use std::io::stdin;
+use std::{collections::HashMap, io::stdin};
 
 use anyhow::{bail, Result};
+use counter::Counter;
 use regex::Regex;
 
-/// solve ax² + bx + c = 0
-fn solve_quadratic(a: f64, b: f64, c: f64) -> (f64, f64) {
-    let r1 = (-b + f64::sqrt(b * b - 4.0 * a * c)) / 2.0 * a;
-    let r2 = (-b - f64::sqrt(b * b - 4.0 * a * c)) / 2.0 * a;
-    (r1, r2)
+#[derive(Debug, PartialEq, Eq, Hash)]
+enum HandType {
+    FiveOfAKind,
+    FourOfAKind,
+    FullHouse,
+    ThreeOfAKind,
+    TwoPair,
+    OnePair,
+    HighCard,
 }
 
-fn parse_input() -> Result<(Vec<i64>, Vec<i64>)> {
-    let numbers = Regex::new(r"(\d+)")?;
-    let mut times = vec![];
-    let mut distances = vec![];
-    for line in stdin().lines().map_while(Result::ok) {
-        if line.starts_with("Time:") {
-            times = numbers
-                .captures_iter(&line.replace(' ', ""))
-                .map(|c| c.get(1).unwrap().as_str().parse())
-                .map_while(Result::ok)
-                .collect();
-        } else if line.starts_with("Distance:") {
-            distances = numbers
-                .captures_iter(&line.replace(' ', ""))
-                .map(|c| c.get(1).unwrap().as_str().parse())
-                .map_while(Result::ok)
-                .collect();
-        } else {
-            bail!("unexpected line: {}", line);
+fn hand_type(hand: &str) -> HandType {
+    let counter_without_joker: Counter<char> = hand.chars().filter(|c| *c != 'J').collect();
+    if counter_without_joker.is_empty() {
+        // it's JJJJJ
+        return HandType::FiveOfAKind;
+    }
+    let hand = hand.replace(
+        'J',
+        &counter_without_joker
+            .k_most_common_ordered(1)
+            .first()
+            .unwrap()
+            .0
+            .to_string(),
+    );
+    let counter: Counter<char> = hand.chars().collect();
+    if counter.keys().len() == 1 {
+        return HandType::FiveOfAKind;
+    }
+    if counter.keys().len() == 2 {
+        if counter.k_most_common_ordered(1)[0].1 == 4 {
+            return HandType::FourOfAKind;
+        }
+        if counter.k_most_common_ordered(1)[0].1 == 3 {
+            return HandType::FullHouse;
         }
     }
-    Ok((times, distances))
+    if counter.keys().len() == 3 {
+        if counter.k_most_common_ordered(1)[0].1 == 3 {
+            return HandType::ThreeOfAKind;
+        }
+        if counter.k_most_common_ordered(1)[0].1 == 2 {
+            return HandType::TwoPair;
+        }
+    }
+    if counter.keys().len() == 4 {
+        return HandType::OnePair;
+    }
+    HandType::HighCard
+}
+
+type CmpKey = (u8, u8, u8, u8, u8, u8);
+
+fn hand_cmp_key(hand: &str) -> CmpKey {
+    let hand_strength = HashMap::from([
+        (HandType::FiveOfAKind, 7u8),
+        (HandType::FourOfAKind, 6u8),
+        (HandType::FullHouse, 5u8),
+        (HandType::ThreeOfAKind, 4u8),
+        (HandType::TwoPair, 3u8),
+        (HandType::OnePair, 2u8),
+        (HandType::HighCard, 1u8),
+    ]);
+    let card_strength: HashMap<char, u8> = "AKQT98765432J"
+        .chars()
+        .enumerate()
+        .map(|(i, c)| (c, (14 - i) as u8))
+        .collect();
+
+    let mut r = vec![*hand_strength.get(&hand_type(hand)).unwrap()];
+    r.extend(hand.chars().map(|c| card_strength.get(&c).unwrap()));
+
+    (r[0], r[1], r[2], r[3], r[4], r[5])
 }
 
 fn main() -> Result<()> {
-    let (times, distances) = parse_input()?;
+    let mut bids = vec![];
+    for line in stdin().lines().map_while(Result::ok) {
+        let parts: Vec<&str> = line.split_whitespace().collect();
+        let hand = parts[0];
+        let bid: i64 = parts[1].parse().unwrap();
+        println!("{} {:?} {}", hand, hand_type(hand), bid);
 
-    if times.len() != distances.len() {
-        bail!(
-            "times has {} elements, but distances has {} elements",
-            times.len(),
-            distances.len()
-        );
+        bids.push((hand.to_owned(), bid));
     }
-
-    let mut prod = 1;
-    for i in 0..times.len() {
-        let t = times[i];
-        let d = distances[i];
-
-        // the equation to solve is x * (t - x) - d = 0
-        //  = t*x - x*x - d = 0
-        //  = -1x² + tx - d = 0
-        let (r1, r2) = solve_quadratic(-1.0, t as f64, -d as f64);
-        let r1 = (r1 + 1.0).floor() as i64;
-        let r2 = (r2 - 1.0).ceil() as i64;
-
-        let ways = (r2 - r1) + 1;
-
-        println!("{t} {d}");
-        println!("ways: {ways}");
-        prod *= ways;
+    bids.sort_by_key(|(hand, _)| hand_cmp_key(hand));
+    let mut winnings = 0;
+    for (i, b) in bids.iter().enumerate() {
+        let (_, bid) = b;
+        winnings += (i as i64 + 1) * bid;
     }
-
-    println!("{prod}");
+    println!("{}", winnings);
     Ok(())
 }
 
 #[cfg(test)]
 mod tests {
+    use super::*;
 
     #[test]
-    fn test() {}
+    fn test_hand_types() {
+        assert_eq!(hand_type("AAAAJ"), HandType::FiveOfAKind);
+        assert_eq!(hand_type("AAAJJ"), HandType::FiveOfAKind);
+        assert_eq!(hand_type("AAJJJ"), HandType::FiveOfAKind);
+        assert_eq!(hand_type("T55J5"), HandType::FourOfAKind);
+        assert_eq!(hand_type("KTJJT"), HandType::FourOfAKind);
+        assert_eq!(hand_type("QQQJA"), HandType::FourOfAKind);
+        assert_eq!(hand_type("2J432"), HandType::ThreeOfAKind);
+        assert_eq!(hand_type("A23J4"), HandType::OnePair);
+        assert_eq!(hand_type("23456"), HandType::HighCard);
+    }
 }