project-euler-100

[RADIOACTIVE] solutions to the first 100 challenges of project euler
git clone git://git.figbert.com/project-euler-100.git
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problem014.py (798B)

      1 # problemName = "Longest Collatz sequence"
      2 # problemNum = 14
      3 # solutionBy = "FIGBERT"
      4 # language = "Python"
      5 # dateCompleted = "06/02/2020"
      6 
      7 def collatz(num):
      8     sequence = 1
      9     while num > 1:
     10         if num % 2 == 0:
     11             num = num//2
     12         else:
     13             num = (3*num) + 1
     14         sequence += 1
     15     return sequence
     16 
     17 if __name__ == "__main__":
     18     answer = [999999, 999999, collatz(999999)]
     19     while answer[0] >= 1:
     20         potential = (answer[0] - 1, collatz(answer[0] - 1))
     21         if potential[1] > answer[2]:
     22             answer[1] = potential[0]
     23             answer[2] = potential[1]
     24         answer[0] = answer[0] - 1
     25     print((
     26         "The starting number, under one million, that produces the "
     27         f"longest chain from the given iterative sequence is {answer[1]}"
     28     ))