13th day

Author: majcn

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 +1,112 @@
+advent_of_code::solution!(13);
+
+use advent_of_code::maneatingape::parse::*;
+
+struct Point {
+    x: i64,
+    y: i64,
+}
+
+impl Point {
+    fn new(x: i64, y: i64) -> Self {
+        Self { x, y }
+    }
+}
+
+struct Machine {
+    a: Point,
+    b: Point,
+    prize: Point,
+}
+
+fn parse_data(input: &str) -> Vec<Machine> {
+    input
+        .split("\n\n")
+        .map(|x| {
+            let mut x_iter = x.iter_signed();
+
+            Machine {
+                a: Point::new(x_iter.next().unwrap(), x_iter.next().unwrap()),
+                b: Point::new(x_iter.next().unwrap(), x_iter.next().unwrap()),
+                prize: Point::new(x_iter.next().unwrap(), x_iter.next().unwrap()),
+            }
+        })
+        .collect()
+}
+
+fn calculate_press(machine: Machine) -> Option<(u64, u64)> {
+    if let Some(b) = calculate_press_b(&machine) {
+        if let Some(a) = calculate_press_a(&machine, b) {
+            return Some((a, b));
+        }
+    }
+
+    None
+}
+
+fn calculate_press_b(machine: &Machine) -> Option<u64> {
+    let top = machine.prize.y * machine.a.x - machine.prize.x * machine.a.y;
+    let bottom = machine.b.y * machine.a.x - machine.a.y * machine.b.x;
+
+    if top % bottom == 0 {
+        Some((top / bottom) as u64)
+    } else {
+        None
+    }
+}
+
+fn calculate_press_a(machine: &Machine, press_b: u64) -> Option<u64> {
+    let top = machine.prize.y - machine.b.y * press_b as i64;
+    let bottom = machine.a.y;
+
+    if top % bottom == 0 {
+        Some((top / bottom) as u64)
+    } else {
+        None
+    }
+}
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let data = parse_data(input);
+
+    let result = data
+        .into_iter()
+        .filter_map(calculate_press)
+        .filter(|&(a, b)| a <= 100 && b <= 100)
+        .fold(0, |acc, (a, b)| acc + a * 3 + b);
+
+    Some(result)
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let data = parse_data(input);
+
+    let result = data
+        .into_iter()
+        .map(|mut machine| {
+            machine.prize.x += 10000000000000;
+            machine.prize.y += 10000000000000;
+            machine
+        })
+        .filter_map(calculate_press)
+        .fold(0, |acc, (a, b)| acc + a * 3 + b);
+
+    Some(result)
+}
+
+#[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));
+    }
+}