Solve 2021/09

2021/day09/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day09"
+version = "0.1.0"

2021/day09/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day09"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

2021/day09/README.md

@@ -0,0 +1,46 @@
+https://adventofcode.com/2021/day/9
+
+## \--- Day 9: Smoke Basin ---
+
+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:
+
+[code]
+
+    2 _1_ 9994321 _0_
+    3987894921
+    98 _5_ 6789892
+    8767896789
+    989996 _5_ 678
+    
+[/code]
+
+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?_
+

2021/day09/input/example0

@@ -0,0 +1,5 @@
+2 _1_ 9994321 _0_
+3987894921
+98 _5_ 6789892
+8767896789
+989996 _5_ 678

2021/day09/input/input

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2021/day09/src/main.rs

@@ -0,0 +1,177 @@
+use std::collections::HashSet;
+use std::io::stdin;
+use std::io::BufRead;
+
+fn main() {
+    let arg = std::env::args().nth(1).unwrap_or("part2".to_string());
+    match arg.as_str() {
+        "part1" => part1(),
+        _ => part2(),
+    }
+}
+
+fn part1() {
+    println!("Part 1");
+    let mut numbers = Vec::new();
+    let mut width = 0;
+    let mut height = 0;
+    for line in stdin().lock().lines() {
+        let line = line.unwrap().replace(" ", "").replace("_", "");
+        width = line.len();
+        println!("{}", line);
+
+        let mut parsed: Vec<u8> = line
+            .chars()
+            .map(|c| c.to_string().parse().unwrap())
+            .collect();
+        numbers.append(&mut parsed);
+        height += 1;
+    }
+
+    dbg!(width, height);
+
+    let field = Field::new(numbers, width, height);
+
+    let mut risk_level: i32 = 0;
+
+    for x in 0..height {
+        for y in 0..width {
+            let value = field.get((x, y));
+            let neighbors = field.neighbors((x, y));
+            if neighbors.iter().all(|&n| n > value) {
+                risk_level += 1 + *value as i32;
+                print!("\x1b[31m{}\x1b[0m", value);
+            } else {
+                print!("{}", value);
+            }
+        }
+        println!();
+    }
+
+    dbg!(risk_level);
+}
+
+fn part2() {
+    println!("Part 2");
+    let mut numbers = Vec::new();
+    let mut width = 0;
+    let mut height = 0;
+    for line in stdin().lock().lines() {
+        let line = line.unwrap().replace(" ", "").replace("_", "");
+        width = line.len();
+        println!("{}", line);
+
+        let mut parsed: Vec<u8> = line
+            .chars()
+            .map(|c| c.to_string().parse().unwrap())
+            .collect();
+        numbers.append(&mut parsed);
+        height += 1;
+    }
+
+    dbg!(width, height);
+
+    let field = Field::new(numbers, width, height);
+
+    let mut basin_sizes = Vec::new();
+
+    for x in 0..height {
+        for y in 0..width {
+            let value = field.get((x, y));
+            let neighbors = field.neighbors((x, y));
+            if neighbors.iter().all(|&n| n > value) {
+                basin_sizes.push(field.basin_size((x, y)));
+                print!("\x1b[31m{}\x1b[0m", value);
+            } else if *value == 9 {
+                print!("\x1b[33m{}\x1b[0m", value);
+            } else {
+                print!("\x1b[37m{}\x1b[0m", value);
+            }
+        }
+        println!();
+    }
+
+    basin_sizes.sort();
+    dbg!(&basin_sizes);
+
+    let solution = basin_sizes.iter().rev().take(3).fold(1, |acc, el| acc * el);
+    dbg!(solution);
+}
+
+struct Field {
+    width: usize,
+    height: usize,
+    numbers: Vec<u8>,
+}
+
+impl<'a> Field {
+    fn new(numbers: Vec<u8>, width: usize, height: usize) -> Field {
+        Field {
+            width,
+            height,
+            numbers,
+        }
+    }
+
+    fn get(&'a self, pos: (usize, usize)) -> &'a u8 {
+        let (x, y) = pos;
+        let idx = x * self.width + y;
+        self.numbers.get(idx).unwrap()
+    }
+
+    fn neighbor_coords(&'a self, pos: (usize, usize)) -> Vec<(usize, usize)> {
+        let (x, y) = pos;
+        let mut coords = Vec::new();
+        let is_top = x == 0;
+        let is_bot = x == self.height - 1;
+        let is_left = y % self.width == 0;
+        let is_right = (y + 1) % self.width == 0;
+
+        if !is_top {
+            coords.push((x - 1, y));
+        }
+        if !is_bot {
+            coords.push((x + 1, y));
+        }
+        if !is_left {
+            coords.push((x, y - 1))
+        }
+        if !is_right {
+            coords.push((x, y + 1))
+        }
+        coords
+    }
+
+    fn neighbors(&'a self, pos: (usize, usize)) -> Vec<&'a u8> {
+        self.neighbor_coords(pos)
+            .iter()
+            .map(|&pos| self.get(pos))
+            .collect()
+    }
+
+    fn basin_size(&self, pos: (usize, usize)) -> i32 {
+        let mut size = 0;
+        let mut coords_to_check = HashSet::new();
+        let mut coords_checked = HashSet::new();
+
+        coords_to_check.insert(pos);
+
+        while !coords_to_check.is_empty() {
+            let pos = *coords_to_check.iter().next().unwrap();
+            coords_to_check.remove(&pos);
+            coords_checked.insert(pos);
+            if *self.get(pos) == 9 {
+                continue;
+            }
+            size += 1;
+            let neighbor_set = HashSet::from_iter(self.neighbor_coords(pos));
+            coords_to_check.extend(&neighbor_set - &coords_checked);
+            // for neighbor in self.neighbor_coords(pos) {
+            //     if !coords_checked.contains(neighbor){
+            //         coords_to_check.add(neighbor)
+            //     }
+            // }
+        }
+        size
+    }
+}