AoC_2020/src/day12.rs

use aoc_runner_derive::{aoc, aoc_generator};

#[derive(Debug)]
pub enum Direction {
    North,
    East,
    South,
    West
}

impl Direction {
    fn from_int(n: i64) -> Self {
        match n%4 {
            0 => Self::East,
            1 => Self::South,
            2 => Self::West,
            3 => Self::North,
            _ => unreachable!()
        }
    }
}

#[derive(Debug)]
pub enum Command {
    Direction(Direction,i64),
    Left(i64),
    Right(i64),
    Forward(i64)
}

#[derive(Debug)]
pub struct Ship {
    rot: i64,
    pos: (i64,i64),
    wp: (i64,i64)
}

impl Ship {
    fn new() -> Self {
        Self {
            rot:0,
            pos: (0,0),
            wp: (10,1)
        }
    }

    fn facing(&self) -> Direction {
        Direction::from_int(self.rot)
    }

    fn cmd_p1(&mut self, cmd: &Command) {
        match cmd {
            Command::Direction(Direction::North,n) => {
                self.pos.1+=n;
            }
            Command::Direction(Direction::South,n) => {
                self.pos.1-=n;
            }
            Command::Direction(Direction::East,n) => {
                self.pos.0+=n;
            }
            Command::Direction(Direction::West,n) => {
                self.pos.0-=n;
            }
            Command::Left(n) => {
                self.rot-=n;
            }
            Command::Right(n) => {
                self.rot+=n;
            }
            Command::Forward(n) => {
                self.cmd_p1(&Command::Direction(self.facing(),*n))
            }
        }
    }

    fn cmd_p2(&mut self, cmd: &Command) {
        match cmd {
            Command::Direction(Direction::North,n) => {
                self.wp.1+=n;
            }
            Command::Direction(Direction::South,n) => {
                self.wp.1-=n;
            }
            Command::Direction(Direction::East,n) => {
                self.wp.0+=n;
            }
            Command::Direction(Direction::West,n) => {
                self.wp.0-=n;
            }
            Command::Right(n) => {
                let wp=self.wp;
                self.wp=match n%4 {
                    0 => wp,
                    1 => (wp.1,-wp.0),
                    2 => (-wp.0,-wp.1),
                    3 => (-wp.1,wp.0),
                    _ => unreachable!()
                };
            }
            Command::Left(n) => {
                let wp=self.wp;
                self.wp=match n%4 {
                    0 => wp,
                    1 => (-wp.1,wp.0),
                    2 => (-wp.0,-wp.1),
                    3 => (wp.1,-wp.0),
                    _ => unreachable!()
                };
            }
            Command::Forward(n) => {
                self.pos.0+=self.wp.0*n;
                self.pos.1+=self.wp.1*n;
            }
        }
    }
}

#[aoc_generator(day12)]
pub fn input_generator(input: &str) -> Vec<Command> {
    input
        .lines()
        .map(|l| {
            let mut chars=l.chars();
            let cmd=chars.next().unwrap();
            let num = chars.collect::<String>().parse().unwrap();
            match cmd {
                'N' => Command::Direction(Direction::North, num),
                'S' => Command::Direction(Direction::South,num),
                'E' => Command::Direction(Direction::East,num),
                'W' => Command::Direction(Direction::West,num),
                'L' if num%90==0 => Command::Left((num/90)%4),
                'R' if num%90==0 => Command::Right((num/90)%4),
                'F' => Command::Forward(num),
                _ => panic!("Invalid command: {}",l)
            }
        }).collect::<Vec<Command>>()
}

#[aoc(day12, part1)]
pub fn solve_part1(input: &Vec<Command>) -> usize {
    let mut ship=Ship::new();
    for cmd in input {
        ship.cmd_p1(cmd);
    }
    return (ship.pos.0.abs() as usize) + (ship.pos.1.abs() as usize);
}

#[aoc(day12, part2)]
pub fn solve_part2(input: &Vec<Command>) -> usize {
    let mut ship=Ship::new();
    for cmd in input {
        ship.cmd_p2(cmd);
    }
    return (ship.pos.0.abs() as usize) + (ship.pos.1.abs() as usize);
}