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CTimmerman/CollatzConjecture3n+1.py

Created July 31, 2021 10:15
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Collatz conjecture
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CollatzConjecture3n+1.py
"""Collatz conjecture. Inspired by https://www.youtube.com/watch?v=094y1Z2wpJg
2021-07-31 by Cees Timmerman
"""
def collatz(n: int) -> int:
return 3*n+1 if n%2 else n//2
def collatz_count(start: int) -> int:
step = 0
while True:
if start == 1:
return step
step += 1
start = collatz(start)
if __name__ == "__main__":
# 1e309+ is float infinity on Python 3.8.5 (tags/v3.8.5:580fbb0, Jul 20 2020, 15:57:54) [MSC v.1924 64 bit (AMD64)] so use 10**309+ integer which is also more accurate.
print(collatz_count(10**30000)) # 523,760 steps. Less than the minimum of 186,000,000,000 claimed on https://youtu.be/094y1Z2wpJg?t=660 which is enough proof for me.
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