From c473ee4fc798f0499aff2c13874d6bc0c9234a8a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Christian=20Gr=C3=BCnhage?=
 <jan.christian@gruenhage.xyz>
Date: Sat, 11 Dec 2021 14:47:15 +0100
Subject: [PATCH] implement day 11

---
 src/day_11/mod.rs     | 67 ++++++++++++++++++++++++++++++++++
 src/day_11/model.rs   | 85 +++++++++++++++++++++++++++++++++++++++++++
 src/day_11/parsing.rs | 14 +++++++
 src/lib.rs            |  1 +
 4 files changed, 167 insertions(+)
 create mode 100644 src/day_11/mod.rs
 create mode 100644 src/day_11/model.rs
 create mode 100644 src/day_11/parsing.rs

diff --git a/src/day_11/mod.rs b/src/day_11/mod.rs
new file mode 100644
index 0000000..61fd5bd
--- /dev/null
+++ b/src/day_11/mod.rs
@@ -0,0 +1,67 @@
+mod model;
+mod parsing;
+
+use aoc_runner_derive::{aoc, aoc_generator};
+pub use model::OctopusGrid;
+pub use parsing::parse_octopus_grid;
+use yap::IntoTokens;
+
+#[aoc_generator(day11)]
+pub fn parse_input(input: &str) -> OctopusGrid {
+    parse_octopus_grid(&mut input.into_tokens()).unwrap()
+}
+
+#[aoc(day11, part1)]
+pub fn part1(input: &OctopusGrid) -> usize {
+    let mut grid = input.clone();
+    let mut sum = 0;
+    for _ in 0..100 {
+        sum += grid.step();
+    }
+    sum
+}
+
+#[aoc(day11, part2)]
+pub fn part2(input: &OctopusGrid) -> usize {
+    let mut grid = input.clone();
+    let mut counter = 0;
+    loop {
+        counter += 1;
+        if grid.step() == 100 {
+            return counter;
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    const EXAMPLE_INPUT: &str = "5483143223
+2745854711
+5264556173
+6141336146
+6357385478
+4167524645
+2176841721
+6882881134
+4846848554
+5283751526";
+    const RESULT_PART_1: usize = 1656;
+    const RESULT_PART_2: usize = 195;
+
+    #[test]
+    fn part1_example() {
+        let result = super::part1(&super::parse_input(EXAMPLE_INPUT));
+        assert_eq!(result, RESULT_PART_1);
+    }
+
+    #[test]
+    fn part2_example() {
+        let result = super::part2(&super::parse_input(EXAMPLE_INPUT));
+        assert_eq!(result, RESULT_PART_2);
+    }
+
+    #[test]
+    fn parse_example() {
+        super::parse_input(EXAMPLE_INPUT);
+    }
+}
diff --git a/src/day_11/model.rs b/src/day_11/model.rs
new file mode 100644
index 0000000..c8ed576
--- /dev/null
+++ b/src/day_11/model.rs
@@ -0,0 +1,85 @@
+use itertools::Itertools;
+
+#[derive(Clone)]
+pub struct OctopusGrid {
+    pub grid: [[u8; 10]; 10],
+}
+
+impl OctopusGrid {
+    pub fn step(&mut self) -> usize {
+        let mut flash_grid: [[bool; 10]; 10] = Default::default();
+        grid_iter().for_each(|(x, y)| self.grid[y][x] += 1);
+        let mut flash_count = 0;
+        loop {
+            grid_iter().for_each(|(x, y)| {
+                if self.grid[y][x] > 9 && !flash_grid[y][x] {
+                    flash_grid[y][x] = true;
+                    surrounding((x, y)).for_each(|(x, y)| self.grid[y][x] += 1);
+                }
+            });
+            let new_flash_count = flash_grid
+                .iter()
+                .flat_map(|col| col.iter())
+                .filter(|val| **val)
+                .count();
+            if new_flash_count == flash_count {
+                break;
+            } else {
+                flash_count = new_flash_count;
+            }
+        }
+        grid_iter().for_each(|(x, y)| {
+            if flash_grid[y][x] {
+                self.grid[y][x] = 0;
+            }
+        });
+        flash_count
+    }
+}
+
+impl ToString for OctopusGrid {
+    fn to_string(&self) -> String {
+        self.grid
+            .iter()
+            .map(|line| line.iter().map(u8::to_string).collect::<String>())
+            .join("\n")
+    }
+}
+
+fn surrounding((x, y): (usize, usize)) -> impl Iterator<Item = (usize, usize)> {
+    let (x, y) = (x as isize, y as isize);
+    (-1..=1)
+        .cartesian_product(-1..=1)
+        .filter_map(move |(x_off, y_off)| {
+            if x + x_off >= 0
+                && x + x_off < 10
+                && y + y_off >= 0
+                && y + y_off < 10
+                && (x_off != 0 || y_off != 0)
+            {
+                Some(((x + x_off) as usize, (y + y_off) as usize))
+            } else {
+                None
+            }
+        })
+}
+
+fn grid_iter() -> impl Iterator<Item = (usize, usize)> {
+    (0..10).cartesian_product(0..10)
+}
+
+#[cfg(test)]
+mod test {
+    use super::OctopusGrid;
+
+    #[test]
+    fn flash() {
+        let mut grid = OctopusGrid {
+            grid: Default::default(),
+        };
+        for _ in 0..9 {
+            assert_eq!(grid.step(), 0);
+        }
+        assert_eq!(grid.step(), 100);
+    }
+}
diff --git a/src/day_11/parsing.rs b/src/day_11/parsing.rs
new file mode 100644
index 0000000..74e4f8a
--- /dev/null
+++ b/src/day_11/parsing.rs
@@ -0,0 +1,14 @@
+use yap::Tokens;
+
+use crate::parsing::{newline, parse_digit, parse_n};
+
+use super::OctopusGrid;
+
+pub fn parse_octopus_grid(tokens: &mut impl Tokens<Item = char>) -> Option<OctopusGrid> {
+    parse_n(
+        tokens,
+        &|t| parse_n(t, &|t| parse_digit(t), &|_| true),
+        &|t| newline(t),
+    )
+    .map(|grid| OctopusGrid { grid })
+}
diff --git a/src/lib.rs b/src/lib.rs
index 5eb57f2..a579490 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -12,5 +12,6 @@ pub mod day_07;
 pub mod day_08;
 pub mod day_09;
 pub mod day_10;
+pub mod day_11;
 
 aoc_lib! { year = 2021 }