55 lines
1.6 KiB
Python
Executable file
55 lines
1.6 KiB
Python
Executable file
#!/usr/bin/env python
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import functools
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import itertools
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import operator
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import sys
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def solve(input: str) -> str:
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def parse(input: str) -> list[int]:
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return [ord(c) for c in input.strip()]
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def compute_sparse_hash(lengths: list[int]) -> list[int]:
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circle = list(range(256))
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cur_pos, skip_size = 0, 0
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for _ in range(64):
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for n in lengths:
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# Invalid length
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assert n < len(circle) # Sanity check
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# Reverse
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for i, j in zip(
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range(cur_pos, cur_pos + n // 2),
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# Avoid off-by-one by going further than necessary
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range(cur_pos + n - 1, cur_pos, -1),
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):
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i %= len(circle)
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j %= len(circle)
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circle[i], circle[j] = circle[j], circle[i]
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# Move
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cur_pos += n + skip_size
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# Increase
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skip_size += 1
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return circle
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def compute_dense_hash(sparse_hash: list[int]) -> list[int]:
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assert len(sparse_hash) == 256 # Sanity check
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return [
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functools.reduce(operator.xor, chunk)
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for chunk in itertools.batched(sparse_hash, 16)
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]
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lengths = parse(input)
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lengths += [17, 31, 73, 47, 23] # Additional lengths
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sparse_hash = compute_sparse_hash(lengths)
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dense_hash = compute_dense_hash(sparse_hash)
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return "".join(f"{n:02x}" for n in dense_hash)
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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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