feat: Day 9 2021 ⭐ 🌟 Rust and TypeScript solution

Author: icyJoseph

2021/day-9/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+authors = ["Joseph Chamochumbi <[email protected]>"]
+edition = "2018"
+name = "day-9"
+version = "0.1.0"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[dependencies]
+aoc = {git = "https://github.com/icyJoseph/advent-of-code.git"}

2021/day-9/src/main.rs

@@ -0,0 +1,166 @@
+use aoc;
+
+fn solve(raw: String) -> () {
+    let rows = raw.trim().split("\n").collect::<Vec<&str>>();
+
+    let height = rows.len();
+    let width = rows[0].len();
+
+    let grid = rows
+        .iter()
+        .flat_map(|row| {
+            row.split("")
+                .filter(|x| !x.is_empty())
+                .map(|c| parse_num::<usize>(c))
+        })
+        .collect::<Vec<usize>>();
+
+    let adj = calc_adj(height, width);
+
+    let mut basins_origins: Vec<usize> = vec![];
+
+    for (index, value) in grid.iter().enumerate() {
+        if adj[index].iter().map(|&m| grid[m]).all(|m| m > *value) {
+            basins_origins.push(index);
+        }
+    }
+
+    println!(
+        "Part One: {}",
+        basins_origins
+            .iter()
+            .map(|&origin| grid[origin] + 1)
+            .sum::<usize>()
+    );
+
+    let mut basin_sizes: Vec<usize> = vec![];
+
+    for origin in basins_origins.iter() {
+        let distances = bfs(&adj, height, width, *origin, &grid);
+        let size = distances.iter().filter(|&x| *x > 0).count() + 1;
+
+        basin_sizes.push(size);
+    }
+
+    basin_sizes.sort_by(|a, b| b.cmp(&a));
+
+    println!(
+        "Part Two: {}",
+        basin_sizes[..3].iter().fold(1, |prev, curr| prev * curr)
+    );
+}
+
+fn main() {
+    let input = aoc::get_input(2021, 9);
+
+    // let input = std::fs::read_to_string("").expect("Error reading input");
+
+    solve(input);
+}
+
+// Utilities
+#[allow(dead_code)]
+fn normal(x: usize, y: usize, width: usize) -> usize {
+    x + y * width
+}
+
+#[allow(dead_code)]
+fn rev_normal(norm: usize, width: usize) -> (usize, usize) {
+    (norm % width, norm / width)
+}
+
+#[allow(dead_code)]
+fn parse_num<T: std::str::FromStr>(str: &str) -> T {
+    match str.trim().parse::<T>() {
+        Ok(n) => n,
+        _ => panic!("Error parsing"),
+    }
+}
+#[allow(dead_code)]
+fn to_int(bin: &str) -> u32 {
+    match u32::from_str_radix(bin, 2) {
+        Ok(n) => n,
+        _ => panic!("Error parsing binary to integer"),
+    }
+}
+
+#[allow(dead_code)]
+fn string_vec<T: std::string::ToString>(vec: &Vec<T>, separator: &str) -> String {
+    vec.iter()
+        .map(|x| x.to_string())
+        .collect::<Vec<String>>()
+        .join(separator)
+}
+
+type Adj = Vec<Vec<usize>>;
+
+fn norm(x: usize, y: usize, width: usize) -> usize {
+    x + y * width
+}
+
+fn calc_adj(height: usize, width: usize) -> Adj {
+    let mut adj = vec![vec![]; height * width];
+
+    for y in 0..height {
+        for x in 0..width {
+            let index = norm(x, y, width);
+            if x > 0 {
+                adj[index].push(norm(x - 1, y, width));
+            }
+            if y + 1 < height {
+                adj[index].push(norm(x, y + 1, width));
+            }
+            if x + 1 < width {
+                adj[index].push(norm(x + 1, y, width));
+            }
+            if y > 0 {
+                adj[index].push(norm(x, y - 1, width));
+            }
+        }
+    }
+
+    adj
+}
+
+fn bfs(adj: &Adj, height: usize, width: usize, root: usize, nodes: &Vec<usize>) -> Vec<usize> {
+    let mut distances = vec![0; height * width];
+
+    let mut visited = vec![false; height * width];
+
+    use std::collections::VecDeque;
+    let mut q = VecDeque::new();
+
+    visited[root] = true;
+
+    q.push_back(root);
+    // distance to self is zero
+    distances[root] = 0;
+
+    loop {
+        let next = q.pop_front();
+
+        match next {
+            None => {
+                break;
+            }
+            Some(elem) => {
+                for &vec in adj[elem].iter() {
+                    if visited[vec] {
+                        continue;
+                    }
+
+                    visited[vec] = true;
+
+                    if nodes[vec] == 9usize {
+                        continue;
+                    }
+
+                    distances[vec] = distances[elem] + 1;
+                    q.push_back(vec);
+                }
+            }
+        }
+    }
+
+    distances
+}

2021/deno/day-9.ts

@@ -0,0 +1,147 @@
+const input = await Deno.readTextFile("./input/day-9.in");
+
+// const input = await Deno.readTextFile("./input/example.in");
+
+const rows = input.split("\n");
+
+const height = rows.length;
+const width = rows[0].length;
+
+const grid = rows.map((row) => row.split("").map(Number));
+
+const adj = calcAdj(width, height);
+
+const origins = [];
+
+for (let y = 0; y < height; y++) {
+  for (let x = 0; x < width; x++) {
+    const value = grid[y][x];
+
+    const adjacent = adj[norm(x, y, width)].map((v) => {
+      const { x, y } = invNorm(v, width);
+      return grid[y][x];
+    });
+
+    const isLow = adjacent.every((v) => v > value);
+
+    if (isLow) {
+      origins.push({ x, y });
+    }
+  }
+}
+
+/**
+ * Part One
+ */
+console.log(
+  "Part One:",
+  origins.map(({ x, y }) => grid[y][x] + 1).reduce((a, b) => a + b, 0)
+);
+
+/**
+ * Part Two
+ */
+
+const flatGrid = flatten2dMatrix(grid);
+
+const basins = [];
+
+for (const { x, y } of origins) {
+  const distances = bfs(norm(x, y, width), adj, flatGrid, width * height);
+  const size = distances.filter((x) => x > 0).length + 1;
+
+  basins.push(size);
+}
+
+basins.sort((a, b) => b - a);
+
+console.log(
+  "Part Two:",
+  basins.slice(0, 3).reduce((a, b) => a * b, 1)
+);
+
+function norm(x: number, y: number, width: number) {
+  return x + y * width;
+}
+
+function invNorm(normal: number, width: number) {
+  return { x: normal % width, y: Math.floor(normal / width) };
+}
+
+function createMatrix<T>(size: number, init: () => T): T[] {
+  return Array.from({ length: size }, init);
+}
+
+function flatten2dMatrix<T>(matrix: T[][]): T[] {
+  const result: T[] = [];
+
+  for (let y = 0; y < matrix.length; y++) {
+    const row = matrix[y];
+    result.push(...row);
+  }
+
+  return result;
+}
+
+function calcAdj(width: number, height: number) {
+  const adj = createMatrix<number[]>(width * height, () => []);
+
+  for (let y = 0; y < height; y++) {
+    for (let x = 0; x < width; x++) {
+      let index = norm(x, y, width);
+      if (x > 0) {
+        // down
+        adj[index].push(norm(x - 1, y, width));
+      }
+      if (y + 1 < height) {
+        // right
+        adj[index].push(norm(x, y + 1, width));
+      }
+      if (x + 1 < width) {
+        // left
+        adj[index].push(norm(x + 1, y, width));
+      }
+      if (y > 0) {
+        // up
+        adj[index].push(norm(x, y - 1, width));
+      }
+    }
+  }
+
+  return adj;
+}
+
+export function bfs(
+  start: number,
+  adj: number[][],
+  grid: number[],
+  size: number
+) {
+  const q: number[] = [];
+  const visited = createMatrix(size, () => false);
+  const distance = createMatrix(size, () => 0);
+
+  visited[start] = true;
+  distance[start] = 0;
+  q.push(start);
+
+  while (true) {
+    const current = q.shift();
+
+    if (current == null) break;
+
+    for (const vec of adj[current]) {
+      if (visited[vec]) continue;
+
+      visited[vec] = true;
+
+      if (grid[vec] === 9) continue;
+
+      distance[vec] = distance[current] + 1;
+
+      q.push(vec);
+    }
+  }
+
+  return distance;
+}