Solve 2021 day 20, 21, 23, 25

2021/d20.py

@@ -0,0 +1,51 @@
+from lib import get_data
+
+data = get_data(__file__)
+
+for rounds in [2, 50]:
+    algo, img = data.strip().split("\n\n")
+    algo = algo.replace("\n", "")
+
+    xs = set()
+    img = img.splitlines()
+    for row in range(len(img)):
+        for col in range(len(img[0])):
+            if img[row][col] == "#":
+                xs.add((row, col))
+
+    for i in range(rounds):
+        y_min = min(v[0] for v in xs) - 6
+        y_max = max(v[0] for v in xs) + 6
+        x_min = min(v[1] for v in xs) - 6
+        x_max = max(v[1] for v in xs) + 6
+
+        nxs = set()
+        for row in range(y_min, y_max + 1):
+            for col in range(x_min, x_max + 1):
+                bin = ""
+                for ro in range(3):
+                    for co in range(3):
+                        if (row + ro, col + co) in xs:
+                            bin += "1"
+                        else:
+                            bin += "0"
+                bin = int(bin, 2)
+                if algo[bin] == "#":
+                    nxs.add((row, col))
+
+        xs = nxs
+        y_min_trim = y_min + 7
+        y_max_trim = y_max - 8
+        x_min_trim = x_min + 7
+        x_max_trim = x_max - 8
+
+        # special clean-up required because input creates pixels when there
+        # are no other pixels around (0b0_0000_0000)
+        if i % 2 == 1:
+            xs = [
+                (r, c)
+                for (r, c) in xs
+                if y_min_trim <= r <= y_max_trim and x_min_trim <= c <= x_max_trim
+            ]
+
+    print(len(xs))