adventofcode2023/day3/rust/src/main.rs

struct Number {
    value: usize,
}

enum Symbol {
    Asterisk,
    Other,
}

enum Tile<'a> {
    Number(&'a Number),
    Symbol(Symbol),
    Period,
}

fn main() {
    let stdin = std::io::stdin();

    let mut map: Vec<Vec<Tile>> = Vec::new();

    for line in stdin.lines() {
        let line = line.unwrap();

        let mut num = Vec::new();
        let mut v = Vec::new();
        for char in line.chars() {
            if !char.is_digit(10) && num.len() > 0 {
                let s: String = num.iter().collect();

                let number = Box::leak(Box::new(Number {
                    value: s.parse().unwrap(),
                }));

                for _ in 0..s.len() {
                    v.push(Tile::Number(number));
                }

                num.clear();
            }

            if char == '.' {
                v.push(Tile::Period);
            } else if char == '*' {
                v.push(Tile::Symbol(Symbol::Asterisk));
            } else if char.is_digit(10) {
                num.push(char);
            } else {
                v.push(Tile::Symbol(Symbol::Other));
            }
        }

        if num.len() > 0 {
            let s: String = num.iter().collect();

            let number = Box::leak(Box::new(Number {
                value: s.parse().unwrap(),
            }));

            for _ in 0..s.len() {
                v.push(Tile::Number(number));
            }
        }
        map.push(v);
    }

    // Part 1
    let mut part1 = 0;

    for (x, row) in map.iter().enumerate() {
        let mut already_added = false;
        for (y, tile) in row.iter().enumerate() {
            match tile {
                Tile::Number(number) => {
                    if already_added {
                        continue;
                    };

                    for dx in -1i32..=1 {
                        for dy in -1i32..=1 {
                            let ix = x.wrapping_add(dx as usize);
                            let iy = y.wrapping_add(dy as usize);
                            if let Some(v) = map.get(ix) {
                                if let Some(Tile::Symbol(_)) = v.get(iy) {
                                    already_added = true;
                                    part1 += number.value;
                                }
                            }
                            if already_added {
                                break;
                            };
                        }
                        if already_added {
                            break;
                        };
                    }
                }
                _ => {
                    if already_added {
                        already_added = false;
                    }
                }
            }
        }
    }

    println!("{}", part1);

    // Part 2
    let mut part2 = 0;

    for (x, row) in map.iter().enumerate() {
        for (y, tile) in row.iter().enumerate() {
            if let Tile::Symbol(Symbol::Asterisk) = tile {
                let mut gears = [None; 2];
                let mut gear_num = 0;
                let mut skip = false;

                for dx in -1i32..=1 {
                    for dy in -1i32..=1 {
                        let ix = x.wrapping_add(dx as usize);
                        let iy = y.wrapping_add(dy as usize);
                        if let Some(v) = map.get(ix) {
                            if let Some(Tile::Number(number)) = v.get(iy) {
                                if let Some(gear) = gears[0] {
                                    if std::ptr::eq(gear, *number) {
                                        continue;
                                    }
                                }
                                if let Some(gear) = gears[1] {
                                    if std::ptr::eq(gear, *number) {
                                        continue;
                                    }
                                }

                                if gear_num == 2 {
                                    skip = true;
                                    break;
                                }

                                gears[gear_num] = Some(*number);
                                gear_num += 1;
                            }
                        }
                    }
                    if skip {
                        break;
                    }
                }

                if gear_num == 2 {
                    unsafe {
                        part2 += (*gears[0].unwrap()).value * (*gears[1].unwrap()).value;
                    }
                }
            }
        }
    }

    println!("{}", part2);
}