clueless

y2021/p20.py

+def enhance(pos, cache={}):
+    seq = tuple(image.get(pos + d, infinity) for d in D9)
+    key = infinity, seq
+    if key not in cache:
+        cache[key] = alg[int(''.join({'.':'0', '#':'1'}[x] for x in seq), 2)]
+    return cache[key]
+
+
+text = open(0).read()
+alg, text = text.split('\n\n')
+D9 =  [dx + dy for dy in [-1j, 0, 1j] for dx in [-1, 0, 1]]
+
+image = {}
+for y, line in enumerate(text.splitlines()):
+    for x, char in enumerate(line):
+        image[complex(x, y)] = char
+
+X, Y = x, y
+for i in range(1, 50 + 1):
+    infinity =  '#.'[i % 2]
+    image = {(x + y * 1j): enhance(x + y * 1j)
+        for x in range(0 - 2 * i, X + 2 * i)
+        for y in range(0 - 2 * i, Y + 2 * i)
+    }
+    if i in {2, 50}:
+        print(sum(v == '#' for v in image.values()))