day 11

3 files changed, 131 insertions, 0 deletions

diff --git a/data/2021/11.txt b/data/2021/11.txt
new file mode 100644
index 0000000..cfbdc33
--- /dev/null
+++ b/data/2021/11.txt
@@ -0,0 +1,10 @@
+5421451741
+3877321568
+7583273864
+3451717778
+2651615156
+6377167526
+5182852831
+4766856676
+3437187583
+3633371586
diff --git a/src/2021/11/mod.rs b/src/2021/11/mod.rs
new file mode 100644
index 0000000..8b3370a
--- /dev/null
+++ b/src/2021/11/mod.rs
@@ -0,0 +1,117 @@
+fn adjacent(
+    i: usize,
+    j: usize,
+    max_i: usize,
+    max_j: usize,
+) -> Vec<(usize, usize)> {
+    let mut ret = vec![];
+    if i > 0 {
+        if j > 0 {
+            ret.push((i - 1, j - 1));
+        }
+        ret.push((i - 1, j));
+        if j < max_j {
+            ret.push((i - 1, j + 1));
+        }
+    }
+    if j > 0 {
+        ret.push((i, j - 1));
+    }
+    if j < max_j {
+        ret.push((i, j + 1));
+    }
+    if i < max_i {
+        if j > 0 {
+            ret.push((i + 1, j - 1));
+        }
+        ret.push((i + 1, j));
+        if j < max_j {
+            ret.push((i + 1, j + 1));
+        }
+    }
+    ret
+}
+
+fn iterate(map: &mut Vec<Vec<(i64, bool)>>) -> i64 {
+    let mut flashes = 0;
+    for line in map.iter_mut() {
+        for (cell, _) in line.iter_mut() {
+            *cell += 1;
+        }
+    }
+
+    loop {
+        let mut new_flashes = 0;
+        for i in 0..map.len() {
+            for j in 0..map[0].len() {
+                if map[i][j].1 {
+                    continue;
+                }
+                if map[i][j].0 > 9 {
+                    map[i][j].1 = true;
+                    new_flashes += 1;
+                    for (i, j) in
+                        adjacent(i, j, map.len() - 1, map[0].len() - 1)
+                    {
+                        map[i][j].0 += 1;
+                    }
+                }
+            }
+        }
+        if new_flashes > 0 {
+            flashes += new_flashes;
+        } else {
+            break;
+        }
+    }
+
+    for line in map.iter_mut() {
+        for (cell, flashed) in line.iter_mut() {
+            if *flashed {
+                *cell = 0;
+                *flashed = false;
+            }
+        }
+    }
+    flashes
+}
+
+pub fn part1() -> anyhow::Result<i64> {
+    let mut map = data_lines!()?
+        .collect::<Result<Vec<String>, _>>()?
+        .iter()
+        .map(|line| {
+            line.bytes()
+                .map(|b| ((b - b'0') as i64, false))
+                .collect::<Vec<_>>()
+        })
+        .collect::<Vec<_>>();
+
+    let mut flashes = 0;
+    for _ in 0..100 {
+        flashes += iterate(&mut map);
+    }
+    Ok(flashes)
+}
+
+pub fn part2() -> anyhow::Result<i64> {
+    let mut map = data_lines!()?
+        .collect::<Result<Vec<String>, _>>()?
+        .iter()
+        .map(|line| {
+            line.bytes()
+                .map(|b| ((b - b'0') as i64, false))
+                .collect::<Vec<_>>()
+        })
+        .collect::<Vec<_>>();
+
+    let mut step = 1;
+    loop {
+        let flashes = iterate(&mut map);
+        if flashes == (map.len() * map[0].len()).try_into()? {
+            break;
+        }
+        step += 1;
+    }
+    Ok(step)
+}
diff --git a/src/2021/mod.rs b/src/2021/mod.rs
index 95346e7..ccac2b0 100644
--- a/src/2021/mod.rs
+++ b/src/2021/mod.rs
@@ -18,6 +18,8 @@ mod day8;
 mod day9;
 #[path = "10/mod.rs"]
 mod day10;
+#[path = "11/mod.rs"]
+mod day11;
 // NEXT MOD
 
 pub fn run(day: u8, puzzle: u8) -> anyhow::Result<i64> {
@@ -42,6 +44,8 @@ pub fn run(day: u8, puzzle: u8) -> anyhow::Result<i64> {
         (9, 2) => day9::part2(),
         (10, 1) => day10::part1(),
         (10, 2) => day10::part2(),
+        (11, 1) => day11::part1(),
+        (11, 2) => day11::part2(),
         // NEXT PART
         _ => Err(anyhow::anyhow!("unknown puzzle {}-{}", day, puzzle)),
     }