83 lines
2 KiB
Python
Executable file
83 lines
2 KiB
Python
Executable file
#!/usr/bin/env python
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import itertools
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import sys
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from typing import Iterator, List, Optional
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def solve(input: List[str]) -> int:
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def find_illegal_char(input: str) -> Optional[int]:
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chunks: List[str] = []
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ends_to_start = {
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")": "(",
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"]": "[",
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"}": "{",
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">": "<",
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}
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for i, c in enumerate(input):
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# Is it a chunk beginning
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if c not in ends_to_start:
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chunks.append(c)
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continue
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# Is it matching the last element on the chunk stack
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current = chunks.pop()
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# If not, corruption has been found
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if ends_to_start[c] != current:
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return i
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return None
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def complete_line(input: str) -> str:
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chunks: List[str] = []
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start_to_end = {
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"(": ")",
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"[": "]",
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"{": "}",
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"<": ">",
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}
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for c in input:
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# Is it a chunk beginning
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if c in start_to_end:
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chunks.append(c)
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continue
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# Otherwise we must match the last open chunk
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assert start_to_end[chunks.pop()] == c # Sanity check
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return "".join(reversed(list(start_to_end[c] for c in chunks)))
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def score_completion(completion: str) -> int:
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char_score = {
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")": 1,
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"]": 2,
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"}": 3,
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">": 4,
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}
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score = 0
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for c in completion:
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score *= 5
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score += char_score[c]
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return score
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def score_completions(completions: Iterator[str]) -> int:
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scores = sorted(map(score_completion, completions))
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return scores[len(scores) // 2]
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incomplete_lines = filter(lambda line: find_illegal_char(line) is None, input)
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completions = map(complete_line, incomplete_lines)
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return score_completions(completions)
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def main() -> None:
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input = [line.strip() for line in sys.stdin.readlines()]
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print(solve(input))
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if __name__ == "__main__":
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main()
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