diff options
| -rw-r--r-- | input12 | 4 | ||||
| -rw-r--r-- | src/main.rs | 126 |
2 files changed, 129 insertions, 1 deletions
@@ -0,0 +1,4 @@ +<x=17, y=-9, z=4> +<x=2, y=2, z=-13> +<x=-1, y=5, z=-1> +<x=4, y=7, z=-7> diff --git a/src/main.rs b/src/main.rs index e482946..c0fa47d 100644 --- a/src/main.rs +++ b/src/main.rs @@ -933,8 +933,132 @@ fn day11() { } } +#[derive(PartialEq, Eq, Clone, Copy)] +struct Position { + x: isize, + y: isize, + z: isize, +} + +#[derive(PartialEq, Eq, Clone, Copy)] +struct Moon { + pos: Position, + velocity: Position, +} + +impl Moon { + fn new(x: isize, y: isize, z: isize) -> Moon { + Moon { + pos: Position { x, y, z }, + velocity: Position { x: 0, y: 0, z: 0 }, + } + } + + fn apply_gravity(&mut self, other: &Moon) { + self.velocity.x += (other.pos.x - self.pos.x).signum(); + self.velocity.y += (other.pos.y - self.pos.y).signum(); + self.velocity.z += (other.pos.z - self.pos.z).signum(); + } + + fn update_position(&mut self) { + self.pos.x += self.velocity.x; + self.pos.y += self.velocity.y; + self.pos.z += self.velocity.z; + } + + fn potential_energy(&self) -> isize { + self.pos.x.abs() + self.pos.y.abs() + self.pos.z.abs() + } + + fn kinetic_energy(&self) -> isize { + self.velocity.x.abs() + self.velocity.y.abs() + self.velocity.z.abs() + } + + fn total_energy(&self) -> isize { + self.potential_energy() * self.kinetic_energy() + } +} + +fn simulate_moons(moons: &mut Vec<Moon>) { + for i in 0..moons.len() { + for j in 0..moons.len() { + let other = moons[j].clone(); + moons[i].apply_gravity(&other); + } + } + for moon in moons { + moon.update_position(); + } +} + +fn gcd(a: isize, b: isize) -> isize { + if b == 0 { + a + } else { + gcd(b, a % b) + } +} + +fn lcm(a: isize, b: isize) -> isize { + (a*b).abs() / gcd(a, b) +} + +fn day12() { + let initial_state = vec![ + Moon::new(17, -9, 4), + Moon::new( 2, 2, -13), + Moon::new(-1, 5, -1), + Moon::new( 4, 7, -7), + ]; + let mut moons = initial_state.clone(); + + for _ in 0..1000 { + simulate_moons(&mut moons); + } + + let total_energy: isize = moons.iter() + .map(|moon| moon.total_energy()) + .sum(); + println!("12a: {}", total_energy); + + let mut period_x = 0; + let initial_x_values: Vec<(isize, isize)> = moons.iter().map(|moon| (moon.pos.x, moon.velocity.x)).collect(); + loop { + period_x += 1; + simulate_moons(&mut moons); + let x_values: Vec<(isize, isize)> = moons.iter().map(|moon| (moon.pos.x, moon.velocity.x)).collect(); + if x_values == initial_x_values { + break; + } + } + + let mut period_y = 0; + let initial_y_values: Vec<(isize, isize)> = moons.iter().map(|moon| (moon.pos.y, moon.velocity.y)).collect(); + loop { + period_y += 1; + simulate_moons(&mut moons); + let y_values: Vec<(isize, isize)> = moons.iter().map(|moon| (moon.pos.y, moon.velocity.y)).collect(); + if y_values == initial_y_values { + break; + } + } + + let mut period_z = 0; + let initial_z_values: Vec<(isize, isize)> = moons.iter().map(|moon| (moon.pos.z, moon.velocity.z)).collect(); + loop { + period_z += 1; + simulate_moons(&mut moons); + let z_values: Vec<(isize, isize)> = moons.iter().map(|moon| (moon.pos.z, moon.velocity.z)).collect(); + if z_values == initial_z_values { + break; + } + } + + println!("12b: {}", lcm(lcm(period_x, period_y), period_z)); +} + fn main() { - day11(); + day12(); } #[cfg(test)] |