AdventOfCode2023/src/bin/day10.rs

use aoc2023_niels_overkamp::common::{self, AOCResult};
use std::collections::HashSet;

const DAY: &str = "day10";

fn main() -> Result<(), Box<dyn std::error::Error>> {
    common::run(DAY, &run)
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum Curvature {
    Right = -1, Straight = 0, Left = 1
}

impl Curvature {
    fn as_number(&self) -> isize {
        *self as isize
    }
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum Direction {
    North, East, South, West
}

impl Direction {
    fn take_pipe(&self, pipe: &u8) -> Option<(Self, Curvature)> {
        match (pipe, self) {
            (b'|', Self::North) => Some((Self::North, Curvature::Straight)),
            (b'|', Self::South) => Some((Self::South, Curvature::Straight)),
            (b'-', Self::West) => Some((Self::West, Curvature::Straight)),
            (b'-', Self::East) => Some((Self::East, Curvature::Straight)),
            (b'L', Self::South) => Some((Self::East, Curvature::Left)),
            (b'L', Self::West) => Some((Self::North,  Curvature::Right)),
            (b'J', Self::South) => Some((Self::West,  Curvature::Right)),
            (b'J', Self::East) => Some((Self::North, Curvature::Left)),
            (b'7', Self::East) => Some((Self::South,  Curvature::Right)),
            (b'7', Self::North) => Some((Self::West, Curvature::Left)),
            (b'F', Self::West) => Some((Self::South, Curvature::Left)),
            (b'F', Self::North) => Some((Self::East,  Curvature::Right)),
            _ => None
        }
    }
    
    fn curvature(&self, other: &Direction) -> Curvature {
        if *self == *other {
            Curvature::Straight
        } else if self.left() == *other {
            Curvature::Left
        } else {
            Curvature::Right
        }
    }
    
    fn do_move(&self, (x, y): (usize, usize)) -> Option<(usize, usize)> {
        match self {
            Self::North => y.checked_sub(1).map(|y| (x, y)),
            Self::East => Some((x + 1, y)),
            Self::South => Some((x, y + 1)),
            Self::West => x.checked_sub(1).map(|x| (x, y))
        }
    }
    
    fn left(&self) -> Self {
        match self {
            Self::North => Self::West,
            Self::East => Self::North,
            Self::South => Self::East,
            Self::West => Self::South
        }
    }
    
    fn right(&self) -> Self {
        match self {
            Self::West => Self::North,
            Self::North => Self::East,
            Self::East => Self::South,
            Self::South => Self::West
        }
    }
}

const DIRECTIONS: [Direction;4] = [Direction::North, Direction::East, Direction::South, Direction::West];

pub fn run(input: &Vec<String>) -> AOCResult {
    let mut start = None;
    'outer: for (y, line) in input.iter().enumerate() {
        for (x, b) in line.as_bytes().iter().enumerate() {
            if *b == b'S' {
                start = Some((x,y));
                break 'outer;
            }
        }
    }
    
    let input: Vec<&[u8]> = input.into_iter().map(|s| s.as_bytes()).collect();

    let (mut x, mut y) = start.ok_or::<Box<dyn std::error::Error>>("No S found in input".into())?;
    let mut start_direction = None;
    
    if let Some(_) = Direction::East.take_pipe(&input[y][x + 1]) {
        start_direction = Some(Direction::East);
    } else if let Some(_) = Direction::South.take_pipe(&input[y + 1][x]) {
        start_direction = Some(Direction::South);
    } else if x > 0 {
        if let Some(_) = Direction::West.take_pipe(&input[y][x - 1]) {
            start_direction = Some(Direction::West);
        }
    } else if y > 0 {
        if let Some(_) = Direction::North.take_pipe(&input[y][x - 1]) {
            start_direction = Some(Direction::North);
        }
    }
    
    let mut direction = start_direction.ok_or::<Box<dyn std::error::Error>>("No valid connection to S found".into())?;
    let start_direction = direction;
    let mut loop_size = 0;
    let mut curvature = 0;
    
    let mut left_outline = HashSet::new();
    let mut line = HashSet::new();
    let mut right_outline = HashSet::new();
    
    
    loop {
        loop_size += 1;
        (x, y) = direction.do_move((x, y)).ok_or_else(|| -> Box<dyn std::error::Error> { format!("Invalid move at {}, {} {:?}", x, y, direction).into() })?;
        line.insert((x,y));
        let pipe = input[y][x];
        let (out_direction, pipe_curvature) = if pipe == b'S' {
            (start_direction, direction.curvature(&start_direction))
        } else {
            direction
                .take_pipe(&pipe)
                .ok_or_else(|| -> Box<dyn std::error::Error> { format!("No valid connection at {}, {} {:?}", x, y, direction).into() })?
        };

//         println!("{}, {}, {:?}-{:?}->{:?}", x, y, direction, pipe_curvature, out_direction);
        match pipe_curvature {
            Curvature::Left => {
                if let Some(coord) = out_direction.right().do_move((x,y)) {
//                     println!("{:?} right", coord);
                    right_outline.insert(coord);
                }
                if let Some(coord) = direction.right().do_move((x,y)) {
//                     println!("{:?} right", coord);
                    right_outline.insert(coord);
                }
            }
            Curvature::Right => {
                if let Some(coord) = out_direction.left().do_move((x,y)) {
//                     println!("{:?} left", coord);
                    left_outline.insert(coord);
                }
                if let Some(coord) = direction.left().do_move((x,y)) {
//                     println!("{:?} left", coord);
                    left_outline.insert(coord);
                }
            }
            Curvature::Straight => ()
        }
        
        direction = out_direction;
        curvature += pipe_curvature.as_number();
        
        if pipe == b'S' {
            break
        }
    }
    
//     println!("{:?}", left_outline);
//     println!("{:?}", right_outline);
//     println!("{:?}", line);
//     println!("{}", curvature);
    
    let outline = if curvature.signum() == (Curvature::Left as isize) {
        left_outline
    } else {
        right_outline
    };
    
    let mut visited = HashSet::new();
    let mut inner_count = 0;
    
    let mut frontier = vec![];
    for coord in outline.into_iter() {
        if visited.contains(&coord) || line.contains(&coord) {
            continue
        }
        frontier.push(coord);
        while let Some(coord) = frontier.pop() {
            if visited.contains(&coord) || line.contains(&coord) {
                continue
            }
            if !line.contains(&coord) {
                println!("{:?} {:?}", coord, visited);
                visited.insert(coord);
                inner_count += 1;
            }
            DIRECTIONS.iter()
                .for_each(|direction| {
                    direction
                        .do_move(coord)
                        .filter(|coord| !visited.contains(coord) && !line.contains(coord))
                        .map(|coord| frontier.push(coord));
                });
        }
    }

    Ok([Some((loop_size / 2).to_string()), Some(inner_count.to_string())])
}

#[test]
pub fn test_day10() {
    assert!(common::run_test(DAY, &run))
}