From 10fb4f2561ed144da2f96a1ebe85b52f8d40b7fd Mon Sep 17 00:00:00 2001 From: Burnus Date: Fri, 21 Apr 2023 14:37:05 +0200 Subject: [PATCH] Added Solution for 2021 day 09 --- 2021/day09_smoke_basin/Cargo.toml | 8 ++ 2021/day09_smoke_basin/challenge.txt | 91 +++++++++++++++ 2021/day09_smoke_basin/src/lib.rs | 113 +++++++++++++++++++ 2021/day09_smoke_basin/tests/challenge_input | 100 ++++++++++++++++ 2021/day09_smoke_basin/tests/sample_input | 5 + 5 files changed, 317 insertions(+) create mode 100644 2021/day09_smoke_basin/Cargo.toml create mode 100644 2021/day09_smoke_basin/challenge.txt create mode 100644 2021/day09_smoke_basin/src/lib.rs create mode 100644 2021/day09_smoke_basin/tests/challenge_input create mode 100644 2021/day09_smoke_basin/tests/sample_input diff --git a/2021/day09_smoke_basin/Cargo.toml b/2021/day09_smoke_basin/Cargo.toml new file mode 100644 index 0000000..94e345b --- /dev/null +++ b/2021/day09_smoke_basin/Cargo.toml @@ -0,0 +1,8 @@ +[package] +name = "day09_smoke_basin" +version = "0.1.0" +edition = "2021" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] diff --git a/2021/day09_smoke_basin/challenge.txt b/2021/day09_smoke_basin/challenge.txt new file mode 100644 index 0000000..e9343af --- /dev/null +++ b/2021/day09_smoke_basin/challenge.txt @@ -0,0 +1,91 @@ +These caves seem to be [lava tubes](https://en.wikipedia.org/wiki/Lava_tube). Parts are even still volcanically active; small hydrothermal vents release smoke into the caves that slowly settles like rain. + +If you can model how the smoke flows through the caves, you might be able to avoid it and be that much safer. The submarine generates a heightmap of the floor of the nearby caves for you (your puzzle input). + +Smoke flows to the lowest point of the area it's in. For example, consider the following heightmap: + +``` +2199943210 +3987894921 +9856789892 +8767896789 +9899965678 + +``` + +Each number corresponds to the height of a particular location, where `9` is the highest and `0` is the lowest a location can be. + +Your first goal is to find the *low points* - the locations that are lower than any of its adjacent locations. Most locations have four adjacent locations (up, down, left, and right); locations on the edge or corner of the map have three or two adjacent locations, respectively. (Diagonal locations do not count as adjacent.) + +In the above example, there are *four* low points, all highlighted: two are in the first row (a `1` and a `0`), one is in the third row (a `5`), and one is in the bottom row (also a `5`). All other locations on the heightmap have some lower adjacent location, and so are not low points. + +The *risk level* of a low point is *1 plus its height*. In the above example, the risk levels of the low points are `2`, `1`, `6`, and `6`. The sum of the risk levels of all low points in the heightmap is therefore `*15*`. + +Find all of the low points on your heightmap. *What is the sum of the risk levels of all low points on your heightmap?* + +Your puzzle answer was `524`. + +\--- Part Two --- +---------- + +Next, you need to find the largest basins so you know what areas are most important to avoid. + +A *basin* is all locations that eventually flow downward to a single low point. Therefore, every low point has a basin, although some basins are very small. Locations of height `9` do not count as being in any basin, and all other locations will always be part of exactly one basin. + +The *size* of a basin is the number of locations within the basin, including the low point. The example above has four basins. + +The top-left basin, size `3`: + +``` +2199943210 +3987894921 +9856789892 +8767896789 +9899965678 + +``` + +The top-right basin, size `9`: + +``` +2199943210 +3987894921 +9856789892 +8767896789 +9899965678 + +``` + +The middle basin, size `14`: + +``` +2199943210 +3987894921 +9856789892 +8767896789 +9899965678 + +``` + +The bottom-right basin, size `9`: + +``` +2199943210 +3987894921 +9856789892 +8767896789 +9899965678 + +``` + +Find the three largest basins and multiply their sizes together. In the above example, this is `9 * 14 * 9 = *1134*`. + +*What do you get if you multiply together the sizes of the three largest basins?* + +Your puzzle answer was `1235430`. + +Both parts of this puzzle are complete! They provide two gold stars: \*\* + +At this point, you should [return to your Advent calendar](/2021) and try another puzzle. + +If you still want to see it, you can [get your puzzle input](9/input). \ No newline at end of file diff --git a/2021/day09_smoke_basin/src/lib.rs b/2021/day09_smoke_basin/src/lib.rs new file mode 100644 index 0000000..637a0ab --- /dev/null +++ b/2021/day09_smoke_basin/src/lib.rs @@ -0,0 +1,113 @@ +use core::fmt::Display; + +#[derive(Debug, PartialEq, Eq)] +pub enum ParseError { + ParseIntError(char), +} + +impl Display for ParseError { + fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { + match self { + Self::ParseIntError(c) => write!(f, "Unable to parse {c} into integer"), + } + } +} + +struct Map { + heights: Vec>, +} + +impl TryFrom<&str> for Map { + type Error = ParseError; + + fn try_from(value: &str) -> Result { + Ok(Self { + heights: value.lines().map(|line| line.chars().map(|c| c.to_digit(10).ok_or(Self::Error::ParseIntError(c)).map(|i| i as usize)).collect::, _>>()).collect::, _>>()?, + }) + } +} + +impl Map { + fn neighbours(&self, (x, y): (usize, usize)) -> Vec<((usize, usize), usize)> { + [(1, 0), (0, 1), (2, 1), (1, 2)].iter().filter(|(dx, dy)| (1..=self.heights[0].len()).contains(&(x+dx)) && (1..=self.heights.len()).contains(&(y+dy))).map(|(dx, dy)| ((x+dx-1, y+dy-1), self.heights[y+dy-1][x+dx-1])).collect() + } + + fn is_local_low_point(&self, (x, y): (usize, usize)) -> bool { + let this_height = self.heights[y][x]; + + self.neighbours((x, y)).iter().all(|(_coords, height)| height > &this_height) + } + + fn get_local_low_points(&self) -> Vec { + self.heights.iter() + .enumerate() + .flat_map(|(y, row)| row.iter() + .enumerate() + .filter(|(x, _height)| self.is_local_low_point((*x, y))) + .map(|(_x, height)| *height) + .collect::>()) + .collect() + } +} + +pub fn run(input: &str) -> Result<(usize, usize), ParseError> { + let mut map = Map::try_from(input)?; + let first = map.get_local_low_points().iter().map(|height| height+1).sum(); + let second = get_largest_basin(&mut map); + Ok((first, second)) +} + +fn get_largest_basin(map: &mut Map) -> usize { + let height = map.heights.len(); + let width = map.heights[0].len(); + + let mut basins = Vec::new(); + + // While it's tempting to only iterate over the local lows from step 1, we cannot garranty that + // every basin contains a local low point (there may be multiple consecutive points forming a + // valley of equal height). Therefore we iterate over the entire array. + (0..height).for_each(|y| { + (0..width).for_each(|x| { + let mut this_basin = 0; + + let mut open_set = vec![(x, y)]; + while let Some((x, y)) = open_set.pop() { + if map.heights[y][x] == 9 { + continue; + } + this_basin += 1; + map.heights[y][x] = 9; + + for neighbour in map.neighbours((x, y)) { + open_set.push(neighbour.0); + } + } + basins.push(this_basin); + }); + }); + + basins.sort_by(|a, b| b.cmp(&a)); + basins.iter().take(3).product() +} + +#[cfg(test)] +mod tests { + use super::*; + use std::fs::read_to_string; + + fn read_file(name: &str) -> String { + read_to_string(name).expect(&format!("Unable to read file: {name}")[..]).trim().to_string() + } + + #[test] + fn test_sample() { + let sample_input = read_file("tests/sample_input"); + assert_eq!(run(&sample_input), Ok((15, 1134))); + } + + #[test] + fn test_challenge() { + let challenge_input = read_file("tests/challenge_input"); + assert_eq!(run(&challenge_input), Ok((524, 1235430))); + } +} diff --git a/2021/day09_smoke_basin/tests/challenge_input b/2021/day09_smoke_basin/tests/challenge_input new file mode 100644 index 0000000..860ccaa --- /dev/null +++ b/2021/day09_smoke_basin/tests/challenge_input @@ -0,0 +1,100 @@ +9987675345698765453987654321234589999899878923493212345678999998656782467898999899878301234578998787 +9876543234789765322398743210123567898789767899986101239899789876543101567897898798763212355989987656 +3987784014897654310987654331235679965697644998765232345997654989765212799956999679854343466799976545 +2199875323998765421298776542346789434595433498754345456789543499876353489549876542975858977899876439 +1012965439899896432359987667457896546789322349987656987898932445987454578932987621986767898943989598 +2125976598798989943467898876589999858899910959898767898976101234598966689431298320987898999432399987 +3234987987656579894578989987679998769999899898769879999965422345679298995420139434598999896543459875 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