feat: solve day 11, part 1 & 2

Cargo.lock

@@ -3,3 +3,12 @@
 [[package]]
 name = "advent-of-code-2021"
 version = "0.1.0"
+dependencies = [
+ "arrayvec",
+]
+
+[[package]]
+name = "arrayvec"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8da52d66c7071e2e3fa2a1e5c6d088fec47b593032b254f5e980de8ea54454d6"

Cargo.toml

@@ -7,3 +7,4 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+arrayvec = "0.7.2"

input/11.txt

@@ -0,0 +1,10 @@
+3265255276
+1537412665
+7335746422
+6426325658
+3854434364
+8717377486
+4522286326
+6337772845
+8824387665
+6351586484

src/day11.rs

@@ -0,0 +1,171 @@
+use arrayvec::ArrayVec;
+
+pub fn parse_input(input: &str) -> [[u32; 10]; 10] {
+    input.lines()
+        .map(|s| s.chars()
+             .map(|s| s.to_digit(10).unwrap())
+             .collect::<ArrayVec<u32, 10>>()
+             .into_inner()
+             .unwrap())
+        .collect::<ArrayVec<[u32; 10], 10>>()
+        .into_inner()
+        .unwrap()
+}
+
+fn display_grid(grid: &[[u32; 10]; 10]) {
+    for i in 0..grid.len() {
+        for j in 0..grid[i].len() {
+            print!("{:X}", grid[i][j]);
+        }
+        print!("\n");
+    }
+    print!("\n");
+}
+
+fn bump_energy(grid: &mut [[u32; 10]; 10]) {
+    for i in 0..grid.len() {
+        for j in 0..grid[i].len() {
+            grid[i][j] += 1;
+        }
+    }
+}
+
+fn bump_energy_around(grid: &mut [[u32; 10]; 10], i: usize, j: usize) {
+    if j > 0 {
+        grid[i+0][j-1] += 1;
+    }
+    if j < 9 {
+        grid[i+0][j+1] += 1;
+    }
+    if i > 0 {
+        grid[i-1][j+0] += 1;
+    }
+    if i < 9 {
+        grid[i+1][j+0] += 1;
+    }
+
+    if i > 0 && j > 0 {
+        grid[i-1][j-1] += 1;
+    }
+    if i < 9 && j > 0 {
+        grid[i+1][j-1] += 1;
+    }
+    if i > 0 && j < 9 {
+        grid[i-1][j+1] += 1;
+    }
+    if i < 9 && j < 9 {
+        grid[i+1][j+1] += 1;
+    }
+}
+
+fn perform_flashes(grid: &mut [[u32; 10]; 10]) -> u32 {
+    let mut flashes = 0;
+    let mut has_flashed: [[bool; 10]; 10] = [[false; 10]; 10];
+    let mut anyone_flashed = true;
+
+    while anyone_flashed {
+        anyone_flashed = false;
+
+        for i in 0..grid.len() {
+            for j in 0..grid[i].len() {
+                if grid[i][j] > 9 && !has_flashed[i][j] {
+                    flashes += 1;
+                    has_flashed[i][j] = true;
+                    anyone_flashed = true;
+                    bump_energy_around(grid, i, j);
+                }
+            }
+        }
+    }
+
+    return flashes;
+}
+
+fn reset_energy(grid: &mut [[u32; 10]; 10]) {
+    for i in 0..grid.len() {
+        for j in 0..grid[i].len() {
+            if grid[i][j] > 9 {
+                grid[i][j] = 0;
+            }
+        }
+    }
+}
+
+fn do_step(grid: &mut [[u32; 10]; 10]) -> u32 {
+    bump_energy(grid);
+    let flashes = perform_flashes(grid);
+    reset_energy(grid);
+    return flashes;
+}
+
+fn has_all_zeros(grid: &[[u32; 10]; 10]) -> bool {
+    for i in 0..grid.len() {
+        for j in 0..grid[i].len() {
+            if grid[i][j] != 0 {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+pub fn part1(grid: &[[u32; 10]; 10]) -> u32 {
+    let mut flashes = 0;
+    let mut active_grid = grid.clone();
+    for _ in 0..100 {
+        flashes += do_step(&mut active_grid);
+    }
+    return flashes;
+}
+
+pub fn part2(grid: &[[u32; 10]; 10]) -> u32 {
+    let mut active_grid = grid.clone();
+    let mut step = 0;
+    while !has_all_zeros(&active_grid) {
+        do_step(&mut active_grid);
+        step += 1;
+    }
+    return step;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_example() {
+        let input = [
+            [5, 4, 8, 3, 1, 4, 3, 2, 2, 3],
+            [2, 7, 4, 5, 8, 5, 4, 7, 1, 1],
+            [5, 2, 6, 4, 5, 5, 6, 1, 7, 3],
+            [6, 1, 4, 1, 3, 3, 6, 1, 4, 6],
+            [6, 3, 5, 7, 3, 8, 5, 4, 7, 8],
+            [4, 1, 6, 7, 5, 2, 4, 6, 4, 5],
+            [2, 1, 7, 6, 8, 4, 1, 7, 2, 1],
+            [6, 8, 8, 2, 8, 8, 1, 1, 3, 4],
+            [4, 8, 4, 6, 8, 4, 8, 5, 5, 4],
+            [5, 2, 8, 3, 7, 5, 1, 5, 2, 6]
+       ];
+        let result = part1(&input);
+        assert_eq!(result, 1656);
+    }
+
+    #[test]
+    fn part2_example() {
+        let input = [
+            [5, 4, 8, 3, 1, 4, 3, 2, 2, 3],
+            [2, 7, 4, 5, 8, 5, 4, 7, 1, 1],
+            [5, 2, 6, 4, 5, 5, 6, 1, 7, 3],
+            [6, 1, 4, 1, 3, 3, 6, 1, 4, 6],
+            [6, 3, 5, 7, 3, 8, 5, 4, 7, 8],
+            [4, 1, 6, 7, 5, 2, 4, 6, 4, 5],
+            [2, 1, 7, 6, 8, 4, 1, 7, 2, 1],
+            [6, 8, 8, 2, 8, 8, 1, 1, 3, 4],
+            [4, 8, 4, 6, 8, 4, 8, 5, 5, 4],
+            [5, 2, 8, 3, 7, 5, 1, 5, 2, 6]
+       ];
+        let result = part2(&input);
+        assert_eq!(result, 195);
+    }
+}
+

src/main.rs

@@ -8,6 +8,7 @@ mod day7;
 mod day8;
 mod day9;
 mod day10;
+mod day11;
 
 use std::{env, process};
 use std::fs::File;
@@ -44,6 +45,8 @@ fn run(day: i32, part: i32, input_filename: &str) {
         "9.2" => println!("{}", day9::part2(day9::parse_input(&contents))),
         "10.1" => println!("{}", day10::part1(&day10::parse_input(&contents))),
         "10.2" => println!("{}", day10::part2(&day10::parse_input(&contents))),
+        "11.1" => println!("{}", day11::part1(&day11::parse_input(&contents))),
+        "11.2" => println!("{}", day11::part2(&day11::parse_input(&contents))),
         _ => println!("Day {} part {} not found", day, part)
     }
 }