45 lines
1.3 KiB
Python
Executable file
45 lines
1.3 KiB
Python
Executable file
#!/usr/bin/env python
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import collections
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import sys
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from collections.abc import Iterator
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def solve(input: str) -> int:
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def parse(input: str) -> tuple[dict[str, list[str]], str]:
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raw_replacements, molecule = input.strip().split("\n\n")
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res: dict[str, list[str]] = collections.defaultdict(list)
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for start, end in (
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line.split(" => ") for line in raw_replacements.splitlines()
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):
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res[start].append(end)
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return res, molecule
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def replace_needle(input: str, needle: str, to: str) -> Iterator[str]:
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assert needle in input # Sanity check
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i = input.find(needle)
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while i != -1:
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yield input[:i] + to + input[i + len(needle) :]
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i = input.find(needle, i + 1)
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def do_replacements(
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replacements: dict[str, list[str]], molecule: str
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) -> Iterator[str]:
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for needle, vals in replacements.items():
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if needle not in molecule:
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continue
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for to in vals:
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yield from replace_needle(molecule, needle, to)
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replacements, molecule = parse(input)
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new_molecules = set(do_replacements(replacements, molecule))
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return len(new_molecules)
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def main() -> None:
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input = sys.stdin.read()
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print(solve(input))
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if __name__ == "__main__":
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main()
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