day 13 pt 1

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 +1,87 @@
+use itertools::Itertools;
+use regex::Regex;
+
+advent_of_code::solution!(13);
+
+#[derive(Debug, Copy, Clone)]
+struct Point<T> {
+    x: T,
+    y: T
+}
+
+#[derive(Debug, Copy, Clone)]
+struct Machine {
+    a_button: Point<u32>,
+    b_button: Point<u32>,
+    prize: Point<u32>
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let r_button = Regex::new(r"Button (A|B): X\+(\d+), Y\+(\d+)").unwrap();
+    let r_prize = Regex::new(r"Prize: X=(\d+), Y=(\d+)").unwrap();
+
+    let machines = input.lines().chunks(4).into_iter().map(|chunk| {
+        let lines = chunk.collect_vec();
+        assert!(lines.len() >= 3);
+
+        let c_a = r_button.captures(lines[0]).unwrap();
+        let a_button = Point { x: c_a[2].parse::<u32>().unwrap(), y: c_a[3].parse::<u32>().unwrap() };
+
+        let c_b = r_button.captures(lines[1]).unwrap();
+        let b_button = Point { x: c_b[2].parse::<u32>().unwrap(), y: c_b[3].parse::<u32>().unwrap() };
+
+        let c_p = r_prize.captures(lines[2]).unwrap();
+        let prize = Point { x: c_p[1].parse::<u32>().unwrap(), y: c_p[2].parse::<u32>().unwrap() };
+
+        Machine { a_button, b_button, prize }
+    }).collect_vec();
+
+    // println!("MACHINES {:?}", machines);
+    // BRUTE FORCE SOLUTION
+    let total_tokens: u32 = machines.iter().map(|machine| {
+        let matches = find_matches(*machine).collect_vec();
+        let min = matches.iter().map(|(x, y)| 3 * x + y).min().unwrap_or(0);
+        // println!("MATCHES {:?}", matches);
+        min
+    }).sum();
+
+    Some(total_tokens)
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    None
+}
+
+// TODO figure out how to reference-ify this
+fn find_matches(machine: Machine) -> impl Iterator<Item=(u32, u32)> {
+    let result = (0..=100).flat_map(move |a_presses| {
+        (0..=100).filter_map(move |b_presses| {
+            let pos_x = machine.a_button.x * a_presses + machine.b_button.x * b_presses;
+            let pos_y = machine.a_button.y * a_presses + machine.b_button.y * b_presses;
+            if pos_x == machine.prize.x && pos_y == machine.prize.y {
+                // println!("FOUND POINT! ({}, {})", pos_x, pos_y);
+                Some((a_presses, b_presses))
+            } else {
+                None
+            }
+        })
+    });
+    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, None);
+    }
+}