feat: day 13

README.md

@@ -40,8 +40,9 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 10](./src/bin/10.rs) | `530.9µs` | `284.2µs` |
 | [Day 11](./src/bin/11.rs) | `238.7µs` | `12.7ms` |
 | [Day 12](./src/bin/12.rs) | `7.5ms` | `8.2ms` |
+| [Day 13](./src/bin/13.rs) | `363.7µs` | `344.0µs` |
 
-**Total: 464.87ms**
+**Total: 465.58ms**
 <!--- benchmarking table --->
 
 ---

data/examples/13.txt

@@ -0,0 +1,15 @@
+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

src/bin/13.rs

@@ -0,0 +1,85 @@
+use regex::Regex;
+advent_of_code::solution!(13);
+
+#[derive(Debug)]
+struct Machine {
+    a: (isize, isize),
+    b: (isize, isize),
+    prize: (isize, isize),
+}
+
+pub fn solve(input: &str, offset: isize) -> Option<u64> {
+    let re = Regex::new(r"\d+").unwrap();
+    Some(
+        input
+            .split("\n\n")
+            .map(|machine| {
+                let numbers: Vec<Vec<isize>> = machine
+                    .lines()
+                    .map(|line| {
+                        re.captures_iter(line)
+                            .map(|cap| cap[0].parse::<isize>().unwrap())
+                            .collect::<Vec<_>>()
+                    })
+                    .collect();
+                Machine {
+                    a: (numbers[0][0], numbers[0][1]),
+                    b: (numbers[1][0], numbers[1][1]),
+                    prize: (numbers[2][0] + offset, numbers[2][1] + offset),
+                }
+            })
+            .map(|machine| {
+                let (a1, b1, c1) = (machine.a.0, machine.b.0, machine.prize.0);
+                let (a2, b2, c2) = (machine.a.1, machine.b.1, machine.prize.1);
+                let (b3, c3) = (a2 * b1, a2 * c1);
+                let (b4, c4) = (a1 * b2, a1 * c2);
+                let (mut b5, mut c5) = (b4 - b3, c4 - c3);
+                if b5 < 0 && c5 < 0 {
+                    b5 = -b5;
+                    c5 = -c5;
+                }
+                if b5 < 0 || c5 < 0 {
+                    return 0;
+                }
+                if c5 % b5 != 0 {
+                    return 0;
+                }
+                let b6 = c5 / b5;
+                let b7 = c1 - b1 * b6;
+                if b7 < 0 {
+                    return 0;
+                }
+                if b7 % a1 != 0 {
+                    return 0;
+                }
+                let a6 = b7 / a1;
+                a6 * 3 + b6
+            })
+            .sum::<isize>() as u64,
+    )
+}
+
+pub fn part_one(input: &str) -> Option<u64> {
+    solve(input, 0)
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    solve(input, 10000000000000)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(480));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(875318608908));
+    }
+}