advent-of-code/source/day_13/mod.rs

use std::collections::HashSet;

use color_eyre::{eyre::eyre, Result};
use itertools::Itertools;

mod canvas;

use canvas::{Canvas, Fold, Point};

pub fn solve() -> Result<()> {
  let input_data = include_str!("../../data/day_13.txt").trim();
  println!("Day 13 Part 1: {}", part_1(input_data)?);
  println!("Day 13 Part 2:\n{}", part_2(input_data)?);
  Ok(())
}

fn parse(input: &str) -> Result<(Canvas, Vec<Fold>)> {
  let mut canvas = Canvas {
    width: 0,
    height: 0,
    points: HashSet::new(),
  };

  let mut in_folds_section = false;
  let mut folds = vec![];

  for line in input.lines() {
    if line == "" {
      in_folds_section = true;
      continue;
    }

    if in_folds_section {
      let mut split = line.split("=");
      let is_x_axis = split
        .next()
        .map(|s| s.ends_with("x"))
        .ok_or_else(|| eyre!("Invalid line: {}", line))?;

      let amount = split
        .next()
        .map(str::parse)
        .ok_or_else(|| eyre!("Expected number: {}", line))??;

      if is_x_axis {
        folds.push(Fold::Vertical(amount));
      } else {
        folds.push(Fold::Horizontal(amount));
      }
    } else {
      let (x, y) = line
        .split(",")
        .tuples()
        .next()
        .ok_or_else(|| eyre!("Invalid line: {}", line))?;

      let x = x.parse()?;
      let y = y.parse()?;
      if canvas.width < x {
        canvas.width = x;
      }

      if canvas.height < y {
        canvas.height = y;
      }

      canvas.points.insert(Point(x, y));
    }
  }

  Ok((canvas, folds))
}

fn part_1(input: &str) -> Result<usize> {
  let (mut canvas, folds) = parse(input)?;
  canvas = canvas.fold(&folds[0]);
  Ok(canvas.points.into_iter().count())
}

fn part_2(input: &str) -> Result<String> {
  let (mut canvas, folds) = parse(input)?;

  for fold in folds {
    canvas = canvas.fold(&fold);
  }

  Ok(format!("{}", canvas))
}