Day 12 (#10)

MWers · web-flow · commit 9ab842d71380 · 2018-12-11T22:40:21.000-08:00
* Day 12

* Remove .swp

* Add .gitignore
diff --git a/.gitignore b/.gitignore
@@ -0,0 +1,2 @@
+.swp
+.DS_Store
diff --git a/2018/12/input-full.txt b/2018/12/input-full.txt
@@ -0,0 +1,34 @@
+initial state: ###.#..#..##.##.###.#.....#.#.###.#.####....#.##..#.#.#..#....##..#.##...#.###.#.#..#..####.#.##.#
+
+#.... => .
+#.##. => #
+..#.. => .
+#.#.# => .
+.#.## => #
+...## => #
+##... => #
+###.. => #
+#..## => .
+.###. => .
+###.# => #
+..... => .
+#..#. => .
+.#.#. => #
+##..# => #
+.##.. => .
+...#. => .
+#.### => .
+..### => .
+####. => .
+#.#.. => #
+.##.# => #
+.#... => #
+##.#. => #
+....# => .
+..#.# => #
+#...# => #
+..##. => .
+.#..# => #
+.#### => .
+##### => #
+##.## => #
diff --git a/2018/12/input-sample.txt b/2018/12/input-sample.txt
@@ -0,0 +1,16 @@
+initial state: #..#.#..##......###...###
+
+...## => #
+..#.. => #
+.#... => #
+.#.#. => #
+.#.## => #
+.##.. => #
+.#### => #
+#.#.# => #
+#.### => #
+##.#. => #
+##.## => #
+###.. => #
+###.# => #
+####. => #
diff --git a/2018/12/solution.py b/2018/12/solution.py
@@ -0,0 +1,52 @@
+from __future__ import print_function
+import re
+
+input_file = 'input-full.txt'
+
+patterns = {}
+pots = ''
+with open(input_file, 'r') as f:
+    raw_data = [i.rstrip() for i in f]
+
+    for line in raw_data:
+        if 'initial state:' in line:
+            pots = ('.' * 10) + line[15:] + ('.' * 120)
+        elif '=>' in line:
+            pattern, action = line.split(' => ')
+            if action == '#':
+                patterns[pattern] = action
+
+# do large number of iterations, look for patterns
+print('{0:>2}: {1}'.format(0, pots))
+for i in range(1, 120):
+    actions = set()
+    for pattern in patterns.keys():
+        action = patterns[pattern]
+        for m in re.finditer('(?={})'.format(re.escape(pattern)), pots):
+            actions.add((m.start() + 2, action))
+    pots = '.' * len(pots)
+    pot_idx_sum = 0
+    for pos, char in actions:
+        pots = pots[:pos] + char + pots[pos+1:]
+        pot_idx_sum += pos - 10
+    print('{0:>2}: {1} {2}'.format(i, pots, pot_idx_sum))
+
+# after 100 generations, a pattern emerges:
+#
+# gen sum
+# --- ----
+# 100 6175
+# 101 6225
+# 102 6275
+# 103 6325
+# 104 6375
+# 105 6425
+# 106 6475
+# 107 6525
+# 108 6575
+# 109 6625
+# 110 6675
+#
+# sum = gen_nbr * 50 + 1175
+part2_sum = 50000000000 * 50 + 1175
+print('part 2: {}'.format(part2_sum))
