1 files changed, 44 insertions, 0 deletions
diff --git a/2021/day11/11b.py b/2021/day11/11b.py
new file mode 100644
index 0000000..18b45d4
--- /dev/null
+++ b/2021/day11/11b.py
@@ -0,0 +1,44 @@
+def adjacent(coord, arr):
+    x, y = coord
+    max_x = len(arr[y]) - 1
+    max_y = len(arr) - 1
+    for dx in [-1, 0, 1]:
+        for dy in [-1, 0, 1]:
+            xp, yp = (x + dx, y + dy)
+            if ((xp, yp) == coord or min(xp, yp) < 0 or xp > max_x or yp > max_y):
+                continue
+            yield (xp, yp)
+
+def flash(coord, arr, flashed):
+    flashed.add(coord)
+    for (x, y) in adjacent(coord, arr):
+        arr[y][x] += 1
+        visit((x, y), arr, flashed)
+
+def visit(coord, arr, flashed):
+    x, y = coord
+    v = arr[y][x]
+    if v > 9 and coord not in flashed:
+        flash(coord, arr, flashed)
+
+def step(arr):
+    flashed = set()
+    for (x,y) in ((x,y) for (y,l) in enumerate(arr) for (x,_) in enumerate(l)):
+        arr[y][x] = arr[y][x] + 1
+        visit((x,y), arr, flashed)
+    for (x,y) in flashed:
+        arr[y][x] = 0
+    return len(flashed)
+
+def print_board(arr):
+    print("\n".join(["".join(map(str, l)) for l in arr]))
+
+state = [[int(n) for n in l] for l in open("./input").read().strip().split("\n")]
+total_squares = sum([len(l) for l in state])
+n = 0
+while True:
+    n += 1
+    if step(state) == total_squares:
+        break
+
+print(n)