day 13 part 1

src/day13.rs

@@ -0,0 +1,72 @@
+use std::{borrow::Borrow, fs::read_to_string};
+
+use itertools::Itertools;
+use regex::Regex;
+
+pub fn day_main() {
+    let input = read_to_string("input/day13.txt").unwrap();
+    let input = input.trim();
+    println!(" part1: {}", part1(input));
+    println!(" part2: {}", part2(input));
+}
+
+type RiddleResult = u64;
+
+fn part1(input: &str) -> RiddleResult {
+    // Button A: X+30, Y+84
+    // Button B: X+74, Y+60
+    // Prize: X=2358, Y=2628
+    let r = Regex::new(
+        r"Button A: X\+(\d+), Y\+(\d+)
+Button B: X\+(\d+), Y\+(\d+)
+Prize: X=(\d+), Y=(\d+)",
+    )
+    .unwrap();
+    r.captures_iter(input)
+        .map(|block| {
+            let (ax, ay, bx, by, px, py) = block
+                .iter()
+                .skip(1)
+                .map(|it| it.unwrap().as_str().parse::<u64>().unwrap())
+                .collect_tuple()
+                .unwrap();
+            let mut solution = None;
+            for a in 0..=100 {
+                for b in 0..=100 {
+                    if a * ax + b * bx == px && a * ay + b * by == py {
+                        let s = 3 * a + b;
+                        if let Some(old) = solution {
+                            if old > s {
+                                solution = Some(s);
+                            }
+                        } else {
+                            solution = Some(s);
+                        }
+                    }
+                }
+            }
+            solution.unwrap_or(0)
+        })
+        .sum()
+}
+
+fn part2(_input: &str) -> RiddleResult {
+    0
+}
+
+#[cfg(test)]
+mod test {
+    use super::{part1, part2};
+
+    const TEST_INPUT: &str = r"";
+
+    #[test]
+    fn test1() {
+        assert_eq!(part1(TEST_INPUT), 0);
+    }
+
+    #[test]
+    fn test2() {
+        assert_eq!(part2(TEST_INPUT), 0);
+    }
+}