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Forest::parse(lines)?; + let result = forest.best_score(); + Ok(ResultType::Integer(result)) + } +} + +#[derive(Debug, Error)] +enum ForestError { + #[error("Not a legal digit: {0}")] + NoLegalDigit(char), + + #[error("The Forst is not a rectangle")] + NonRectangleForest, + + #[error("Zero Sized Forest not allowed")] + NoZeroSizedForest, +} + +#[derive(Debug)] +struct Forest { + trees: Vec>, + width: usize, + height: usize, +} + +impl Forest { + pub fn create(trees: Vec>) -> Result { + let height = trees.len(); + if height == 0 { + return Err(ForestError::NoZeroSizedForest); + } + let width = trees[0].len(); + if width == 0 { + return Err(ForestError::NoZeroSizedForest); + } + + for row in trees.iter() { + if row.len() != width { + return Err(ForestError::NonRectangleForest); + } + } + + Ok(Forest { + trees, + width, + height, + }) + } + + pub fn parse(lines: &[String]) -> Result { + lines + .iter() + .map(|line| { + line.chars() + .map(|height| height.to_digit(10).ok_or(ForestError::NoLegalDigit(height))) + .collect::, _>>() + }) + .collect::, _>>() + .and_then(Forest::create) + } + + pub fn count_visible(&self) -> i64 { + let mut vis_count = 2 * (self.width + self.height - 2) as i64; + let mut visible = vec![vec![false; self.width - 2]; self.height - 2]; + + for y in 1..self.height - 1 { + let mut talest_seen = self.trees[y][0]; + for x in 1..self.width - 1 { + let tree = self.trees[y][x]; + if tree > talest_seen { + vis_count += 1; + visible[y - 1][x - 1] = true; + talest_seen = self.trees[y][x]; + } + } + + let mut talest_seen = self.trees[y][self.width - 1]; + for x in (1..self.width - 1).rev() { + let tree = self.trees[y][x]; + if tree > talest_seen { + if !visible[y - 1][x - 1] { + vis_count += 1; + visible[y - 1][x - 1] = true; + } + talest_seen = self.trees[y][x]; + } + } + } + + for x in 1..self.width - 1 { + let mut talest_seen = self.trees[0][x]; + for y in 1..self.height - 1 { + let tree = self.trees[y][x]; + if tree > talest_seen { + if !visible[y - 1][x - 1] { + vis_count += 1; + visible[y - 1][x - 1] = true; + } + talest_seen = self.trees[y][x]; + } + } + + let mut talest_seen = self.trees[self.height - 1][x]; + for y in (1..self.height - 1).rev() { + let tree = self.trees[y][x]; + if tree > talest_seen { + if !visible[y - 1][x - 1] { + vis_count += 1; + visible[y - 1][x - 1] = true; + } + talest_seen = self.trees[y][x]; + } + } + } + + vis_count + } + + pub fn best_score(&self) -> i64 { + iproduct!(1..self.width - 1, 1..self.height - 1) + .map(|(x, y)| self.score(x, y)) + .max() + // None can only happen when we have a forrest with no inner trees. + // In that case 0 is the correct solution. + // We already forbid zero height and zero width forests during create. + .unwrap_or(0) + } + + fn score(&self, x: usize, y: usize) -> i64 { + let tree = self.trees[y][x]; + let left = (0..x) + .rev() + .fold_while(0, |acc, x| { + if self.trees[y][x] < tree { + FoldWhile::Continue(acc + 1) + } else { + FoldWhile::Done(acc + 1) + } + }) + .into_inner(); + let right = (x + 1..self.width) + .fold_while(0, |acc, x| { + if self.trees[y][x] < tree { + FoldWhile::Continue(acc + 1) + } else { + FoldWhile::Done(acc + 1) + } + }) + .into_inner(); + let up = (0..y) + .rev() + .fold_while(0, |acc, y| { + if self.trees[y][x] < tree { + FoldWhile::Continue(acc + 1) + } else { + FoldWhile::Done(acc + 1) + } + }) + .into_inner(); + let down = (y + 1..self.height) + .fold_while(0, |acc, y| { + if self.trees[y][x] < tree { + FoldWhile::Continue(acc + 1) + } else { + FoldWhile::Done(acc + 1) + } + }) + .into_inner(); + + left * right * up * down + } +} + +#[cfg(test)] +mod test { + use super::*; + use crate::common::file::read_lines; + use anyhow::Result; + + #[test] + fn test_parse() -> Result<()> { + let day = Day {}; + let lines = read_lines(day.get_day_number(), "example01.txt")?; + let forest = Forest::parse(&lines)?; + assert_eq!(forest.width, 5); + assert_eq!(forest.height, 5); + + Ok(()) + } + + #[test] + fn test_part1() -> Result<()> { + let day = Day {}; + let lines = read_lines(day.get_day_number(), "example01.txt")?; + let expected = ResultType::Integer(21); + let result = day.part1(&lines)?; + assert_eq!(result, expected); + + Ok(()) + } + + #[test] + fn test_part2() -> Result<()> { + let day = Day {}; + let lines = read_lines(day.get_day_number(), "example01.txt")?; + let expected = ResultType::Integer(8); + let result = day.part2(&lines)?; + assert_eq!(result, expected); + + Ok(()) + } +} diff --git a/src/days/mod.rs b/src/days/mod.rs index f1f6a19..703a165 100644 --- a/src/days/mod.rs +++ b/src/days/mod.rs @@ -5,6 +5,7 @@ mod day04; mod day05; mod day06; mod day07; +mod day08; mod template; pub use template::DayTrait; @@ -14,7 +15,7 @@ pub mod day_provider { use super::*; use thiserror::Error; - const MAX_DAY: usize = 7; + const MAX_DAY: usize = 8; pub fn get_day(day_num: usize) -> Result, ProviderError> { match day_num { @@ -25,6 +26,7 @@ pub mod day_provider { 5 => Ok(Box::new(day05::Day)), 6 => Ok(Box::new(day06::Day)), 7 => Ok(Box::new(day07::Day)), + 8 => Ok(Box::new(day08::Day)), _ => Err(ProviderError::InvalidNumber(day_num)), } }