Created
December 12, 2020 06:19
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AOC 2020 Day 12
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pub mod day12 { | |
// (+E/-W, +N/-S) | |
#[derive(Debug, Copy, Clone)] | |
pub struct Point(f32, f32); | |
#[derive(Debug)] | |
pub struct State { | |
current: Point, | |
heading: Point | |
} | |
impl State { | |
fn rotate_heading(&mut self, angle_change: f32) { | |
let rads = angle_change.to_radians(); | |
let last_heading = self.heading; | |
self.heading.0 = (rads.sin() * last_heading.1 + rads.cos() * last_heading.0).round(); | |
self.heading.1 = (rads.cos() * last_heading.1 - rads.sin() * last_heading.0).round(); | |
} | |
} | |
pub fn run(input: &str, initial_heading: Point, part1: bool) -> f32 { | |
let mut state = State { current: Point(0.0, 0.0), heading: initial_heading }; | |
for line in input.lines() { | |
let cmd = line.chars().next().unwrap(); | |
let arg = line[1..].parse::<f32>().unwrap(); | |
match cmd { | |
'E' => if part1 { state.current.0 += arg } else { state.heading.0 += arg }, | |
'W' => if part1 { state.current.0 -= arg } else { state.heading.0 -= arg }, | |
'N' => if part1 { state.current.1 += arg } else { state.heading.1 += arg }, | |
'S' => if part1 { state.current.1 -= arg } else { state.heading.1 -= arg }, | |
'F' => { | |
state.current.0 += arg * state.heading.0; | |
state.current.1 += arg * state.heading.1; | |
}, | |
'L' => state.rotate_heading(-arg as f32), | |
'R' => state.rotate_heading(arg as f32), | |
_ => panic!("Unexpected cmd") | |
} | |
// println!("{} {:?}", line, state); | |
} | |
state.current.0.abs() + state.current.1.abs() | |
} | |
pub fn part1(input: &str) -> f32 { | |
run(input, Point(1.0, 0.0), true) | |
} | |
pub fn part2(input: &str) -> f32 { | |
run(input, Point(10.0, 1.0), false) | |
} | |
} | |
fn main() { | |
let input = std::fs::read_to_string("input.txt").expect("Reading input.txt"); | |
println!("Day 12: {} {}", day12::part1(&input), day12::part2(&input)); | |
} |
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