[2024] Day 13 initial solution

Author: connorslade

README.md

@@ -17,6 +17,7 @@ Thank you to [Eric Wastl](http://was.tl) for running this incredible yearly even
 - [Day 10: Hoof It](aoc_2024/src/day_10.rs)
 - [Day 11: Plutonian Pebbles](aoc_2024/src/day_11.rs)
 - [Day 12: Garden Groups](aoc_2024/src/day_12.rs)
+- [Day 13: Claw Contraption](aoc_2024/src/day_13.rs)
 <!-- MARKER -->
 
 ## [2023](https://adventofcode.com/2023) [![aoc_2023](https://github.com/connorslade/advent-of-code/actions/workflows/aoc_2023.yml/badge.svg)](https://github.com/connorslade/advent-of-code/actions/workflows/aoc_2023.yml)

aoc_2024/src/day_13.rs

@@ -0,0 +1,165 @@
+use std::collections::{HashMap, VecDeque};
+
+use common::{solution, Answer};
+use nd_vec::{vector, Vec2};
+
+solution!("Claw Contraption", 13);
+
+fn part_a(input: &str) -> Answer {
+    let problem = Problem::parse(input);
+    problem
+        .cases
+        .iter()
+        .map(|x| x.cheapest())
+        .filter(|&x| x != u64::MAX)
+        .sum::<u64>()
+        .into()
+}
+
+fn part_b(input: &str) -> Answer {
+    /* i used mathematica for p2
+
+    out = 0;
+    Do[
+      x = input[[i]];
+      solve =
+       Solve[x[[1]][[1]] == x[[2]][[1]]*a + x[[3]][[1]]*b &&
+         x[[1]][[2]] == x[[2]][[2]]*a + x[[3]][[2]]*b, {a, b}, Integers];
+      result = 3*solve[[All, 1, 2]] + solve[[All, 2, 2]];
+      out += If[Length[result] == 0, {0}, result];
+      , {i, 1, Length[input]}];
+    out
+
+    */
+
+    Answer::Unimplemented
+}
+
+#[derive(Debug)]
+struct Problem {
+    cases: Vec<Case>,
+}
+
+#[derive(Debug)]
+struct Case {
+    a_button: Vec2<u64>,
+    b_button: Vec2<u64>,
+    goal: Vec2<u64>,
+}
+
+fn parse_button(input: &str) -> Vec2<u64> {
+    let (_, parts) = input.rsplit_once(": ").unwrap();
+    let (x, y) = parts.split_once(", ").unwrap();
+    vector!(x[1..].parse().unwrap(), y[1..].parse().unwrap())
+}
+
+impl Problem {
+    fn parse(input: &str) -> Self {
+        let cases = input
+            .split("\n\n")
+            .map(|x| {
+                let mut lines = x.split('\n');
+                let a_button = parse_button(lines.next().unwrap());
+                let b_button = parse_button(lines.next().unwrap());
+
+                let (_, prize) = lines.next().unwrap().rsplit_once(": ").unwrap();
+                let (x, y) = prize.split_once(", ").unwrap();
+                let prize = vector!(x[2..].parse().unwrap(), y[2..].parse().unwrap());
+
+                Case {
+                    a_button,
+                    b_button,
+                    goal: prize,
+                }
+            })
+            .collect();
+        Self { cases }
+    }
+
+    fn part_b(mut self) -> Self {
+        for case in self.cases.iter_mut() {
+            case.goal += vector!(10000000000000, 10000000000000);
+        }
+
+        self
+    }
+}
+
+impl Case {
+    fn cheapest(&self) -> u64 {
+        // a->3, b->1
+        fn inner(
+            case: &Case,
+            memo: &mut HashMap<(Vec2<u64>, (u64, u64)), u64>,
+            pos: Vec2<u64>,
+            counts: (u64, u64),
+            price: u64,
+        ) -> u64 {
+            if let Some(&cache) = memo.get(&(pos, counts)) {
+                return cache;
+            }
+
+            if pos == case.goal {
+                return price;
+            }
+
+            if counts.0 > 100 || counts.1 > 100 {
+                return u64::MAX;
+            }
+
+            let min = inner(
+                case,
+                memo,
+                pos + case.a_button,
+                (counts.0 + 1, counts.1),
+                price + 3,
+            )
+            .min(inner(
+                case,
+                memo,
+                pos + case.b_button,
+                (counts.0, counts.1 + 1),
+                price + 1,
+            ));
+
+            memo.insert((pos, counts), min);
+
+            min
+        }
+
+        inner(self, &mut HashMap::new(), vector!(0, 0), (0, 0), 0)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use indoc::indoc;
+
+    const CASE: &str = indoc! {"
+        Button A: X+94, Y+34
+        Button B: X+22, Y+67
+        Prize: X=8400, Y=5400
+
+        Button A: X+26, Y+66
+        Button B: X+67, Y+21
+        Prize: X=12748, Y=12176
+
+        Button A: X+17, Y+86
+        Button B: X+84, Y+37
+        Prize: X=7870, Y=6450
+
+        Button A: X+69, Y+23
+        Button B: X+27, Y+71
+        Prize: X=18641, Y=10279
+    "};
+
+    #[test]
+    fn part_a() {
+        assert_eq!(super::part_a(CASE), 480.into());
+    }
+
+    #[test]
+    fn part_b() {
+        assert_eq!(super::part_b(CASE), ().into());
+    }
+}

aoc_2024/src/lib.rs

@@ -12,6 +12,7 @@ mod day_09;
 mod day_10;
 mod day_11;
 mod day_12;
+mod day_13;
 // [import_marker]
 
 pub const SOLUTIONS: &[Solution] = &[
@@ -27,5 +28,6 @@ pub const SOLUTIONS: &[Solution] = &[
     day_10::SOLUTION,
     day_11::SOLUTION,
     day_12::SOLUTION,
+    day_13::SOLUTION,
     // [list_marker]
 ];