Solutions to day 18.

day-18/input.txt

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day-18/sample.txt

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+.#.#.#
+...##.
+#....#
+..#...
+#.#..#
+####..

day-18/solution.py

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+from __future__ import print_function
+import fileinput
+
+
+def neighbours(x, y, field):
+    alive = 0
+    for i in range(max(x - 1, 0), min(x + 2, len(field))):
+        for j in range(max(y - 1, 0), min(y + 2, len(field))):
+            if i == x and j == y:
+                continue
+
+            if field[i][j]:
+                alive += 1
+
+    return alive
+
+def newState(x, y, field):
+    alive = neighbours(x, y, field)
+    if field[x][y]:
+        return alive == 2 or alive == 3
+
+    return alive == 3
+
+def update(field):
+    newField = []
+    for x in range(len(field)):
+        newField.append([newState(x, y, field) for y in range(len(field))])
+
+    return newField
+
+def enableCorners(field):
+    size = len(field) - 1
+    field[0][0] = field[0][size] = field[size][0] = field[size][size] = True
+
+
+field = []
+for line in fileinput.input():
+    field.append([c == '#' for c in line.strip()])
+
+original = field
+
+for i_ in range(100):
+    field = update(field)
+
+print ("Without corners:", sum([sum(int(y) for y in x) for x in field]))
+
+field = original
+enableCorners(field)
+
+for i_ in range(100):
+    field = update(field)
+    enableCorners(field)
+
+print ("With corners:", sum([sum(int(y) for y in x) for x in field]))