AdventOfCode2022/08/main.rs

#![allow(dead_code)]
use std::fs::File;
use std::io;
use std::io::BufRead;
use std::path::Path;
use std::time::Instant;

#[derive(Debug, Clone, Copy)]
struct Tree(i8, bool); // height, visible from outside

fn main() {
    let now = Instant::now();
    part_one();
    let part_one_duration = now.elapsed();
    part_two();
    let part_two_duration = now.elapsed();
    println!(
        "p1: {}ms, p2: {}ms",
        part_one_duration.as_millis(),
        (part_two_duration - part_one_duration).as_millis()
    );
}

fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>>
where
    P: AsRef<Path>,
{
    // note that this discards a final newline
    let file = File::open(filename)?;
    Ok(io::BufReader::new(file).lines())
}

fn part_one() {
    let mut grid: Vec<Vec<Tree>> = vec![];
    let mut total = 0;
    if let Ok(lines) = read_lines("./inputs/input") {
        for (i, line) in lines.enumerate() {
            if let Ok(row) = line {
                grid.push(vec![]);
                let mut max = -1;
                for c in row.chars() {
                    if (c as i8) - 48 > max {
                        total += 1;
                        max = (c as i8) - 48;
                        grid[i].push(Tree((c as i8) - 48, true));
                    } else {
                        grid[i].push(Tree((c as i8) - 48, false));
                    }
                }
                max = -1;
                let invert = grid[i].len() - 1;
                for (j, t) in grid[i].clone().iter().rev().enumerate() {
                    if t.0 > max {
                        if !grid[i][invert - j].1 {
                            total += 1;
                        }
                        max = t.0;
                        grid[i][invert - j] = Tree(t.0, true);
                    }
                }
            }
        }
    }
    let invert = grid.len() - 1;
    for i in 0..grid.len() {
        let mut in_max = -1;
        let mut out_max = -1;
        for j in 0..grid.len() {
            if grid[j][i].0 > in_max {
                if !grid[j][i].1 {
                    total += 1;
                }
                in_max = grid[j][i].0;
                grid[j][i] = Tree(grid[j][i].0, true);
            }
            if grid[invert - j][i].0 > out_max {
                if !grid[invert - j][i].1 {
                    total += 1;
                }
                out_max = grid[invert - j][i].0;
                grid[invert - j][i] = Tree(grid[invert - j][i].0, true);
            }
        }
    }
    println!("{}", total);
}

fn part_two() {
    let mut grid: Vec<Vec<Tree>> = vec![];
    let mut best = 0;
    if let Ok(lines) = read_lines("./inputs/input") {
        for (i, line) in lines.enumerate() {
            if let Ok(row) = line {
                grid.push(vec![]);
                for c in row.chars() {
                    grid[i].push(Tree((c as i8) - 48, false));
                }
            }
        }
    }
    // alright, we'll do this the hard way
    // we can skip the edges, because they all multiply by 0 in one way or another
    for i in 1..grid.len() - 1 {
        for j in 1..grid.len() - 1 {
            let (mut score, mut acc) = (1, 0); // a base score and the counter we'll reuse
            for x in (0..j).rev() {
                // left
                acc += 1;
                if grid[i][x].0 >= grid[i][j].0 {
                    break;
                }
            }
            score *= acc;
            acc = 0;
            for x in (0..i).rev() {
                // up
                acc += 1;
                if grid[x][j].0 >= grid[i][j].0 {
                    break;
                }
            }
            score *= acc;
            acc = 0;
            for x in (j + 1)..grid.len() {
                // right
                acc += 1;
                if grid[i][x].0 >= grid[i][j].0 {
                    break;
                }
            }
            score *= acc;
            acc = 0;
            for x in (i + 1)..grid.len() {
                // down
                acc += 1;
                if grid[x][j].0 >= grid[i][j].0 {
                    break;
                }
            }
            score *= acc;
            if score > best {
                best = score;
            }
        }
    }
    println!("{}", best);
}