star twenty five

2026-01-01 07:21:35 -05:00 · 2024-12-13 21:36:36 -05:00
parent d186c82690
commit e3cf8d2606
2 changed files with 247 additions and 0 deletions
--- a/src/main.rs
+++ b/src/main.rs
@@ -24,6 +24,7 @@ mod star_twenty_one;
 mod star_twenty_two;
 mod star_twenty_three;
 mod star_twenty_four;
+mod star_twenty_five;

 fn main() {
    let args: Vec<String> = env::args().collect();
@@ -52,6 +53,7 @@ fn main() {
        "22" => star_twenty_two::run(),
        "23" => star_twenty_three::run(),
        "24" => star_twenty_four::run(),
+        "25" => star_twenty_five::run(),
        _ => unreachable!(),
    }
 }
--- a/src/star_twenty_five.rs
+++ b/src/star_twenty_five.rs
@@ -0,0 +1,245 @@
+use std::fs;
+
+pub fn run() {
+    let file = fs::read_to_string("./inputs/star_twenty_five.txt").unwrap();
+    let machines = parse_input(file.lines());
+
+    println!("{:?}", solve_all_machines(&machines));
+
+}
+
+#[derive(PartialEq, Debug, Clone)]
+struct MachineSettings {
+    a_button: (isize, isize),
+    b_button: (isize, isize),
+    prize_location: (isize, isize)
+}
+
+fn parse_input<'a, I>(str_lines: I) -> Vec<MachineSettings>
+where
+    I: IntoIterator<Item = &'a str>
+{
+    let mut machines = vec![];
+    let mut machine = MachineSettings {
+        a_button: (0, 0),
+        b_button: (0, 0),
+        prize_location: (0, 0)
+    };
+
+    for line in str_lines {
+        let line = String::from(line);
+        if line.starts_with("Button A") {
+            machine.a_button = get_xy(&line);
+        } else if line.starts_with("Button B") {
+            machine.b_button = get_xy(&line);
+        } else if line.starts_with("Prize") {
+            machine.prize_location = get_xy(&line);
+            machines.push(machine.clone());
+            machine = MachineSettings {
+                a_button: (0, 0),
+                b_button: (0, 0),
+                prize_location: (0, 0)
+            };
+        }
+    }
+
+    machines
+}
+
+
+fn get_xy(string: &String) -> (isize, isize) {
+    let mut split = string.split(",");
+    let x_string = split.next().unwrap().chars().filter(|s| "0123456789".contains(*s)).collect::<String>().to_string();
+    let y_string = split.next().unwrap().chars().filter(|s| "0123456789".contains(*s)).collect::<String>().to_string();
+    (x_string.parse::<isize>().unwrap(), y_string.parse::<isize>().unwrap())
+}
+
+fn solve_all_machines(machines: &Vec<MachineSettings>) -> isize {
+    machines.iter()
+        .map(|machine| solve_machine(machine))
+        .map(|solution| solution.unwrap_or(0))
+        .sum()
+}
+
+// failed bruteforce attempt
+// fn find_optimal_plays(x: isize, y: isize, machine: &MachineSettings, tokens_used: usize, a_presses: usize, b_presses: usize) -> (bool, usize) {
+//     if a_presses > 100 || b_presses > 100 {
+//         return (false, usize::MAX);
+//     }
+//     if x > machine.prize_location.0 || y > machine.prize_location.1 {
+//         return (false, usize::MAX);
+//     }
+//     if x == machine.prize_location.0 && y == machine.prize_location.1 {
+//         return (true, tokens_used)
+//     }
+
+//     if x < machine.prize_location.0 && y < machine.prize_location.1 {
+//         // push B button
+//         let (is_prize_found, found_tokens_used) = find_optimal_plays(
+//             x + machine.b_button.0,
+//             y + machine.b_button.1,
+//             machine,
+//             tokens_used + 1,
+//             a_presses,
+//             b_presses + 1,
+//         );
+//         if is_prize_found {
+//             return (true, found_tokens_used);
+//         }
+//         // push A button
+//         return find_optimal_plays(
+//             x + machine.a_button.0,
+//             y + machine.a_button.1,
+//             machine,
+//             tokens_used + 3,
+//             a_presses + 1,
+//             b_presses,
+//         );
+//     }
+
+//     (false, usize::MAX)
+// }
+
+fn solve_machine(machine: &MachineSettings) -> Option<isize> {
+    // Applying Cramer's rule
+
+    let d = (machine.a_button.0 * machine.b_button.1) - (machine.a_button.1 * machine.b_button.0);
+    if d == 0 {
+        return None;
+    }
+
+    let dx = (machine.prize_location.0 * machine.b_button.1) - (machine.prize_location.1 * machine.b_button.0);
+    let dy = (machine.prize_location.1 * machine.a_button.0) - (machine.prize_location.0 * machine.a_button.1);
+
+    if dx % d != 0 || dy % d != 0 {
+        return None;
+    }
+
+    let a = dx / d;
+    let b = dy / d;
+
+    if a < 0 || b < 0 || a > 100 || b > 100 {
+        return None;
+    }
+
+
+    if (a * machine.a_button.0) + (b * machine.b_button.0) != machine.prize_location.0 ||
+       (a * machine.a_button.1) + (b * machine.b_button.1) != machine.prize_location.1 {
+        return None;
+    }
+
+    Some((a * 3) + (b * 1))
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_parse_input() {
+        let input = vec![
+            "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",
+        ].join("\n");
+        let result = parse_input(input.lines());
+        assert_eq!(
+            result,
+            [
+                MachineSettings {
+                    a_button: (94, 34),
+                    b_button: (22, 67),
+                    prize_location: (8400, 5400),
+                },
+                MachineSettings {
+                    a_button: (26, 66),
+                    b_button: (67, 21),
+                    prize_location: (12748, 12176),
+                },
+                MachineSettings {
+                    a_button: (17, 86),
+                    b_button: (84, 37),
+                    prize_location: (7870, 6450),
+                },
+                MachineSettings {
+                    a_button: (69, 23),
+                    b_button: (27, 71),
+                    prize_location: (18641, 10279),
+                },
+            ],
+        );
+
+    }
+
+    #[test]
+    fn test_solve_machine() {
+        let machine = MachineSettings {
+            a_button: (94, 34),
+            b_button: (22, 67),
+            prize_location: (8400, 5400),
+        };
+        assert_eq!(solve_machine(&machine), Some(280));
+
+        let machine = MachineSettings {
+            a_button: (26, 66),
+            b_button: (67, 21),
+            prize_location: (12748, 12176),
+        };
+        assert_eq!(solve_machine(&machine), None);
+
+        let machine = MachineSettings {
+            a_button: (17, 86),
+            b_button: (84, 37),
+            prize_location: (7870, 6450),
+        };
+        assert_eq!(solve_machine(&machine), Some(200));
+
+        let machine = MachineSettings {
+            a_button: (69, 23),
+            b_button: (27, 71),
+            prize_location: (18641, 10279),
+        };
+        assert_eq!(solve_machine(&machine), None);
+    }
+
+    #[test]
+    fn test_solve_all_machines() {
+        let machines = vec![
+            MachineSettings {
+                a_button: (94, 34),
+                b_button: (22, 67),
+                prize_location: (8400, 5400),
+            },
+            MachineSettings {
+                a_button: (26, 66),
+                b_button: (67, 21),
+                prize_location: (12748, 12176),
+            },
+            MachineSettings {
+                a_button: (17, 86),
+                b_button: (84, 37),
+                prize_location: (7870, 6450),
+            },
+            MachineSettings {
+                a_button: (69, 23),
+                b_button: (27, 71),
+                prize_location: (18641, 10279),
+            },
+        ];
+        assert_eq!(solve_all_machines(&machines), 480);
+    }
+}
+