My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2018/12
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2018/day12.py
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2018/day12.py
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import fileinput
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INITIAL = None
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RULES = {}
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GENS = 200 # 200 generations is safe for the automata to converge
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TARGET_GEN = 50000000000
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for i, line in enumerate(fileinput.input()):
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if i == 0:
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INITIAL = line.split()[-1]
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elif i >= 2:
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a, _, b = line.split()
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RULES[a] = b
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state = ['.'] * GENS + list(INITIAL) + ['.'] * GENS
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pot_sums = []
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for it in range(GENS):
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amt = sum(i - GENS for i, p in enumerate(state) if p == '#')
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pot_sums.append(amt)
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next_state = ['.'] * len(state)
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for i in range(len(state) - 2):
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next_state[i + 2] = RULES.get(''.join(state[i:i+5]), '.')
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state = next_state
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print "Sum of plants after 20 generations:", pot_sums[20]
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growth_per_gen = pot_sums[-1] - pot_sums[-2]
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remaining_gens = TARGET_GEN - GENS + 1
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print "Sum after 50000000000 generations:", growth_per_gen * remaining_gens + pot_sums[-1]
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2018/inputs/12.txt
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2018/inputs/12.txt
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initial state: #...####.##..####..#.##....##...###.##.#..######..#..#..###..##.#.###.#####.##.#.#.#.##....#..#..#..
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...## => .
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...#. => #
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....# => .
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###.# => #
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..... => .
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..#.. => .
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#.#.# => .
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#..#. => .
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#...# => .
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##... => .
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.#.#. => #
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.#..# => .
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.###. => .
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#..## => #
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..#.# => #
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.#### => #
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##..# => #
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##.#. => #
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.#... => #
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#.#.. => .
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##### => .
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###.. => #
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.##.# => .
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#.##. => .
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..### => .
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.#.## => #
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..##. => #
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#.### => .
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.##.. => #
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##.## => .
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#.... => .
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####. => #