day13

aoc_2024/src/day13.rs

@@ -0,0 +1,254 @@
+use std::cmp::Ordering;
+
+use aoc_runner_derive::{aoc, aoc_generator};
+use nom::bytes::complete::tag;
+use nom::character::complete::{multispace0, u64 as parse_u64};
+use nom::multi::many0;
+use nom::IResult;
+
+#[derive(Debug, Clone, Copy)]
+struct Case {
+    button_a: (u64, u64),
+    button_b: (u64, u64),
+    prize: (u64, u64),
+}
+
+type Input = Vec<Case>;
+
+#[aoc_generator(day13)]
+fn parse(input: &str) -> Input {
+    many0(parse_case)(input).unwrap().1
+}
+
+fn parse_case(input: &str) -> IResult<&str, Case> {
+    let (input, _) = tag("Button A: X+")(input)?;
+    let (input, button_a_x) = parse_u64(input)?;
+    let (input, _) = tag(", Y+")(input)?;
+    let (input, button_a_y) = parse_u64(input)?;
+    let (input, _) = tag("\nButton B: X+")(input)?;
+    let (input, button_b_x) = parse_u64(input)?;
+    let (input, _) = tag(", Y+")(input)?;
+    let (input, button_b_y) = parse_u64(input)?;
+    let (input, _) = tag("\nPrize: X=")(input)?;
+    let (input, prize_x) = parse_u64(input)?;
+    let (input, _) = tag(", Y=")(input)?;
+    let (input, prize_y) = parse_u64(input)?;
+    let (input, _) = multispace0(input)?;
+
+    Ok((
+        input,
+        Case {
+            button_a: (button_a_x, button_a_y),
+            button_b: (button_b_x, button_b_y),
+            prize: (prize_x, prize_y),
+        },
+    ))
+}
+
+#[aoc(day13, part1)]
+fn part1(input: &Input) -> u64 {
+    input
+        .iter()
+        .copied()
+        .map(|case| {
+            let (vec_low, vec_high, cost_low, cost_high) = match (case.button_a.1 * case.button_b.0)
+                .cmp(&(case.button_a.0 * case.button_b.1))
+            {
+                Ordering::Greater => (case.button_b, case.button_a, 1, 3),
+                Ordering::Less => (case.button_a, case.button_b, 3, 1),
+                Ordering::Equal => panic!("Parallel"),
+            };
+            let vec_prize = case.prize;
+
+            let vec_low_norm = (
+                vec_low.0 as f64 / ((vec_low.0 * vec_low.0 + vec_low.1 * vec_low.1) as f64).sqrt(),
+                vec_low.1 as f64 / ((vec_low.0 * vec_low.0 + vec_low.1 * vec_low.1) as f64).sqrt(),
+            );
+
+            let vec_prize_proj = (
+                vec_low_norm.0
+                    * (vec_prize.0 as f64 * vec_low_norm.0 + vec_prize.1 as f64 * vec_low_norm.1),
+                vec_low_norm.1
+                    * (vec_prize.0 as f64 * vec_low_norm.0 + vec_prize.1 as f64 * vec_low_norm.1),
+            );
+
+            let vec_prize_perp = (
+                vec_prize.0 as f64 - vec_prize_proj.0,
+                vec_prize.1 as f64 - vec_prize_proj.1,
+            );
+
+            let len_prize_perp =
+                (vec_prize_perp.0 * vec_prize_perp.0 + vec_prize_perp.1 * vec_prize_perp.1).sqrt();
+
+            let vec_high_proj = (
+                vec_low_norm.0
+                    * (vec_high.0 as f64 * vec_low_norm.0 + vec_high.1 as f64 * vec_low_norm.1),
+                vec_low_norm.1
+                    * (vec_high.0 as f64 * vec_low_norm.0 + vec_high.1 as f64 * vec_low_norm.1),
+            );
+
+            let vec_high_perp = (
+                vec_high.0 as f64 - vec_high_proj.0,
+                vec_high.1 as f64 - vec_high_proj.1,
+            );
+
+            let len_high_perp =
+                (vec_high_perp.0 * vec_high_perp.0 + vec_high_perp.1 * vec_high_perp.1).sqrt();
+
+            let n_high = len_prize_perp / len_high_perp;
+
+            let vec_low_goal = (
+                vec_prize.0 as f64 - n_high * vec_high.0 as f64,
+                vec_prize.1 as f64 - n_high * vec_high.1 as f64,
+            );
+
+            let len_low = ((vec_low.0 * vec_low.0 + vec_low.1 * vec_low.1) as f64).sqrt();
+
+            let len_low_goal =
+                (vec_low_goal.0 * vec_low_goal.0 + vec_low_goal.1 * vec_low_goal.1).sqrt();
+
+            let n_low = len_low_goal / len_low;
+
+            let n_high = n_high.round() as u64;
+            let n_low = n_low.round() as u64;
+
+            if n_high * vec_high.0 + n_low * vec_low.0 == vec_prize.0
+                && n_high * vec_high.1 + n_low * vec_low.1 == vec_prize.1
+            {
+                n_high * cost_high + n_low * cost_low
+            } else {
+                0
+            }
+        })
+        .sum()
+}
+
+#[aoc(day13, part2)]
+fn part2(input: &Input) -> u64 {
+    input
+        .iter()
+        .copied()
+        .map(|case| {
+            let (vec_low, vec_high, cost_low, cost_high) = match (case.button_a.1 * case.button_b.0)
+                .cmp(&(case.button_a.0 * case.button_b.1))
+            {
+                Ordering::Greater => (case.button_b, case.button_a, 1, 3),
+                Ordering::Less => (case.button_a, case.button_b, 3, 1),
+                Ordering::Equal => panic!("Parallel"),
+            };
+            let vec_prize = (
+                case.prize.0 + 10_000_000_000_000,
+                case.prize.1 + 10_000_000_000_000,
+            );
+
+            let vec_low_norm = (
+                vec_low.0 as f64 / ((vec_low.0 * vec_low.0 + vec_low.1 * vec_low.1) as f64).sqrt(),
+                vec_low.1 as f64 / ((vec_low.0 * vec_low.0 + vec_low.1 * vec_low.1) as f64).sqrt(),
+            );
+
+            let vec_prize_proj = (
+                vec_low_norm.0
+                    * (vec_prize.0 as f64 * vec_low_norm.0 + vec_prize.1 as f64 * vec_low_norm.1),
+                vec_low_norm.1
+                    * (vec_prize.0 as f64 * vec_low_norm.0 + vec_prize.1 as f64 * vec_low_norm.1),
+            );
+
+            let vec_prize_perp = (
+                vec_prize.0 as f64 - vec_prize_proj.0,
+                vec_prize.1 as f64 - vec_prize_proj.1,
+            );
+
+            let len_prize_perp =
+                (vec_prize_perp.0 * vec_prize_perp.0 + vec_prize_perp.1 * vec_prize_perp.1).sqrt();
+
+            let vec_high_proj = (
+                vec_low_norm.0
+                    * (vec_high.0 as f64 * vec_low_norm.0 + vec_high.1 as f64 * vec_low_norm.1),
+                vec_low_norm.1
+                    * (vec_high.0 as f64 * vec_low_norm.0 + vec_high.1 as f64 * vec_low_norm.1),
+            );
+
+            let vec_high_perp = (
+                vec_high.0 as f64 - vec_high_proj.0,
+                vec_high.1 as f64 - vec_high_proj.1,
+            );
+
+            let len_high_perp =
+                (vec_high_perp.0 * vec_high_perp.0 + vec_high_perp.1 * vec_high_perp.1).sqrt();
+
+            let n_high = len_prize_perp / len_high_perp;
+
+            let vec_low_goal = (
+                vec_prize.0 as f64 - n_high * vec_high.0 as f64,
+                vec_prize.1 as f64 - n_high * vec_high.1 as f64,
+            );
+
+            let len_low = ((vec_low.0 * vec_low.0 + vec_low.1 * vec_low.1) as f64).sqrt();
+
+            let len_low_goal =
+                (vec_low_goal.0 * vec_low_goal.0 + vec_low_goal.1 * vec_low_goal.1).sqrt();
+
+            let n_low = len_low_goal / len_low;
+
+            let n_high = n_high.round() as u64;
+            let n_low = n_low.round() as u64;
+
+            if n_high * vec_high.0 + n_low * vec_low.0 == vec_prize.0
+                && n_high * vec_high.1 + n_low * vec_low.1 == vec_prize.1
+            {
+                n_high * cost_high + n_low * cost_low
+            } else {
+                0
+            }
+        })
+        .sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(
+            part1(&parse(
+                "Button A: X+94, Y+34
+Button B: X+22, Y+67
+Prize: X=8400, Y=5400"
+            )),
+            280
+        );
+        assert_eq!(
+            part1(&parse(
+                "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"
+            )),
+            480
+        );
+        assert_eq!(
+            part1(&parse(include_str!("../input/2024/day13.txt").trim_end())),
+            28753
+        );
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(
+            part2(&parse(include_str!("../input/2024/day13.txt").trim_end())),
+            102718967795500
+        );
+    }
+}

aoc_2024/src/lib.rs

@@ -2,6 +2,7 @@ mod day1;
 mod day10;
 mod day11;
 mod day12;
+mod day13;
 mod day2;
 mod day3;
 mod day4;