Day 11

2021/day11.py

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+with open("input11.txt") as f:
+    lines = [line.rstrip() for line in f]
+cells = [list(map(int, line)) for line in lines]
+dim = len(cells)
+
+
+def near(x, y):
+    return (
+        (a, b)
+        for a in range(max(0, x - 1), min(x + 2, dim))
+        for b in range(max(0, y - 1), min(y + 2, dim))
+        if (a, b) != (x, y)
+    )
+
+
+def up(x, y, f):
+    if (x, y) in f:
+        return
+    cells[x][y] += 1
+    if cells[x][y] <= 9:
+        return
+    f.add((x, y))
+    cells[x][y] = 0
+    for nx, ny in near(x, y):
+        up(nx, ny, f)
+
+
+def step():
+    flashed = set()
+    for x, row in enumerate(cells):
+        for y, cell in enumerate(row):
+            up(x, y, flashed)
+    for fx, fy in flashed:
+        cells[fx][fy] = 0
+    return len(flashed)
+
+
+# Part 1
+num_flashes = 0
+for _ in range(100):
+    num_flashes += step()
+print(num_flashes)
+
+# Part 2
+num_steps = 100
+while sum(sum(row) for row in cells) != 0:
+    step()
+    num_steps += 1
+print(num_steps)