25 lines
941 B
Python
25 lines
941 B
Python
#!/usr/bin/env python3
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import re
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from collections import Counter
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from itertools import groupby
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from operator import itemgetter
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lines = (x.strip() for x in open("input.txt"))
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first = next(lines)
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next(lines)
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repl = (re.match(r"([A-Z]{2}) -> ([A-Z])", line).groups() for line in lines)
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repl = (v for (a, b), insert in repl for v in [(a + insert, a + b), (insert + b, a + b)])
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repl = {k: list(map(itemgetter(1), v)) for k, v in groupby(sorted(repl), itemgetter(0))}
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combinations = Counter(first[a:a+2] for a in range(len(first)-1))
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for _ in range(40):
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combinations = {k: sum_val for k, v in repl.items() if (sum_val := sum(combinations.get(x, 0) for x in v)) > 0}
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letters = ((l, cnt) for key, cnt in combinations.items() for l in key)
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letters = {k: sum(map(itemgetter(1), v)) for k, v in groupby(sorted(letters), itemgetter(0))}
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letters[first[0]] += 1
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letters[first[-1]] += 1
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print((max(letters.values()) - min(letters.values())) // 2)
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