day 13

README.md

@@ -40,6 +40,7 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 10](./src/bin/10.rs) | `464.5µs` | `28.4µs` |
 | [Day 11](./src/bin/11.rs) | `179.0µs` | `9.2ms` |
 | [Day 12](./src/bin/12.rs) | `2.5ms` | `4.7ms` |
+| [Day 13](./src/bin/13.rs) | `63.4µs` | `60.9µs` |
 
-**Total: 310.93ms**
+**Total: 311.05ms**
 <!--- 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 +1,134 @@
+use std::ops::Rem;
+
+use itertools::Itertools;
+
+advent_of_code::solution!(13);
+
+#[derive(Debug, Eq, Hash, PartialEq, Clone, Copy)]
+struct Pos(i64, i64);
+
+#[derive(Debug, Eq, Hash, PartialEq, Clone, Copy)]
+struct Machine {
+    a: Pos,
+    b: Pos,
+    prize: Pos,
+}
+
+pub fn part_one(input: &str) -> Option<i64> {
+    let machines = input
+        .split("\n\n")
+        .map(|maching_def| {
+            let lines = maching_def.trim().lines().collect_vec();
+
+            let ax_idx = lines[0].find("X+").unwrap();
+            let ax: i64 = lines[0][ax_idx + 2..ax_idx + 4].parse().unwrap();
+            let ay_idx = lines[0].find("Y+").unwrap();
+            let ay: i64 = lines[0][ay_idx + 2..ay_idx + 4].parse().unwrap();
+
+            let bx_idx = lines[1].find("X+").unwrap();
+            let bx: i64 = lines[1][bx_idx + 2..bx_idx + 4].parse().unwrap();
+            let by_idx = lines[1].find("Y+").unwrap();
+            let by: i64 = lines[1][by_idx + 2..by_idx + 4].parse().unwrap();
+
+            let px_idx = lines[2].find("X=").unwrap();
+            let pxc_idx = lines[2].find(",").unwrap();
+            let px: i64 = lines[2][px_idx + 2..pxc_idx].parse().unwrap();
+            let py_idx = lines[2].find("Y=").unwrap();
+            let py: i64 = lines[2][py_idx + 2..].parse().unwrap();
+
+            Machine {
+                a: Pos(ax, ay),
+                b: Pos(bx, by),
+                prize: Pos(px, py),
+            }
+        })
+        .collect_vec();
+
+    let mut res = 0;
+    for mach in machines {
+        if let Some(sol) = solve(mach) {
+            res += sol
+        };
+    }
+
+    Some(res)
+}
+
+fn solve(mach: Machine) -> Option<i64> {
+    let determinant = mach.a.0 * mach.b.1 - mach.a.1 * mach.b.0;
+    if determinant == 0 {
+        return None;
+    }
+
+    if (mach.b.1 * mach.prize.0 - mach.b.0 * mach.prize.1).rem(determinant) != 0
+        || (mach.a.0 * mach.prize.1 - mach.a.1 * mach.prize.0).rem(determinant) != 0
+    {
+        return None;
+    }
+
+    let a_clicks = (mach.b.1 * mach.prize.0 - mach.b.0 * mach.prize.1).checked_div(determinant);
+    let b_clicks = (mach.a.0 * mach.prize.1 - mach.a.1 * mach.prize.0).checked_div(determinant);
+
+    if let (Some(a), Some(b)) = (a_clicks, b_clicks) {
+        Some(a * 3 + b)
+    } else {
+        None
+    }
+}
+
+pub fn part_two(input: &str) -> Option<i64> {
+    let machines = input
+        .split("\n\n")
+        .map(|maching_def| {
+            let lines = maching_def.trim().lines().collect_vec();
+
+            let ax_idx = lines[0].find("X+").unwrap();
+            let ax: i64 = lines[0][ax_idx + 2..ax_idx + 4].parse().unwrap();
+            let ay_idx = lines[0].find("Y+").unwrap();
+            let ay: i64 = lines[0][ay_idx + 2..ay_idx + 4].parse().unwrap();
+
+            let bx_idx = lines[1].find("X+").unwrap();
+            let bx: i64 = lines[1][bx_idx + 2..bx_idx + 4].parse().unwrap();
+            let by_idx = lines[1].find("Y+").unwrap();
+            let by: i64 = lines[1][by_idx + 2..by_idx + 4].parse().unwrap();
+
+            let px_idx = lines[2].find("X=").unwrap();
+            let pxc_idx = lines[2].find(",").unwrap();
+            let px: i64 = lines[2][px_idx + 2..pxc_idx].parse().unwrap();
+            let py_idx = lines[2].find("Y=").unwrap();
+            let py: i64 = lines[2][py_idx + 2..].parse().unwrap();
+
+            Machine {
+                a: Pos(ax, ay),
+                b: Pos(bx, by),
+                prize: Pos(px + 10000000000000, py + 10000000000000),
+            }
+        })
+        .collect_vec();
+
+    let mut res = 0;
+    for mach in machines {
+        if let Some(sol) = solve(mach) {
+            res += sol
+        };
+    }
+
+    Some(res)
+}
+
+#[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, None);
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, None);
+    }
+}