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PO
 

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  1. PO
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    <p>After explaining the proposed solution to a colleague, the answer came to me: this solution does not take into consideration the length of sequences generated outside of the range of numbers being tested. Therefore, a new solution will need to be devised that considers the length of complete sequences.</p> <p>To test the algorithm, the following program was written. The method works for a sequence over an entire closed range. This is quite impossible to accomplish in the Collatz Problem, so the code fails.</p> <pre><code>import random import time class Sequencer: def __init__(self, limit, seed): random.seed(seed) self.__sequence = tuple(random.sample(range(limit), limit)) def __call__(self, start): yield from self.__sequence[self.__sequence.index(start):] @property def longest(self): return self.__sequence[0] def main(limit): while True: sequence = Sequencer(limit, str(time.time())) longest = find_longest(limit, sequence) print('Found longest ' + ('' if longest == sequence.longest else 'in') + 'correctly.') def find_longest(limit, sequence): start, found = set(range(limit)), set() while start: number = start.pop() result = set(get_sequence(sequence(number), found)) start -= result found |= result return number def get_sequence(sequence, found): for number in sequence: if number in found: break yield number if __name__ == '__main__': main(1000000) </code></pre> <p>The corrected version of the code follows a similar pattern in its design but keeps track of values outside of the original range. Execution time has been found to be similar to other Python solutions to the puzzle.</p> <pre><code>def main(): start, found = set(range(2, 1000000)), {1: 1} while start: scope = reversed(tuple(sequence(start.pop(), found))) value = dict(map(reversed, enumerate(scope, found[next(scope)] + 1))) start -= frozenset(value) found.update(value) lengths = dict(map(reversed, found.items())) print(lengths[max(lengths)]) def sequence(n, found): while True: yield n if n in found: break n = 3 * n + 1 if n &amp; 1 else n &gt;&gt; 1 if __name__ == '__main__': main() </code></pre>
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    1. POA wrong answer obviously means a logic error, but what is at fault in what was thought?
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    1. USNoctis Skytower
    1. USNoctis Skytower
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    1. This table or related slice is empty.
    1. POA wrong answer obviously means a logic error, but what is at fault in what was thought?
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    1. This table or related slice is empty.
    1. VO
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      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
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      1. This table or related slice is empty.
      1. VTDownMod
    3. VO
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      1. VTAcceptedByOriginator
    1. COI am not convinced that this observation is accurate. Does anyone else have further insight?
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      1. USNoctis Skytower
    2. COI think the just deleted answer about the order being arbitrary was right. There's no reason to assume that the last value in `start` leads to the longest sequence.
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      1. USBlckknght
 

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