Python/maths/3n+1.py
Sanders Lin 1e0b33d3dd Update 3n+1.py (#996)
* Update 3n+1.py

Made variable names more meaningful and removed nested functions.

* Update 3n+1.py

* Update 3n+1.py

* Update 3n+1.py
2019-07-13 09:04:43 +02:00

31 lines
757 B
Python

from typing import Tuple, List
def n31(a: int) -> Tuple[List[int], int]:
"""
Returns the Collatz sequence and its length of any postiver integer.
>>> n31(4)
([4, 2, 1], 3)
"""
if not isinstance(a, int):
raise TypeError('Must be int, not {0}'.format(type(a).__name__))
if a < 1:
raise ValueError('Given integer must be greater than 1, not {0}'.format(a))
path = [a]
while a != 1:
if a % 2 == 0:
a = a // 2
else:
a = 3*a +1
path += [a]
return path, len(path)
def main():
num = 4
path , length = n31(num)
print("The Collatz sequence of {0} took {1} steps. \nPath: {2}".format(num,length, path))
if __name__ == '__main__':
main()