<reponame>Coalemus/Python-Projects<filename>automatewithpython/.practiceprojects/collatzsequence.py
#!/bin/zsh

'''
is even, then collatz()
should print number // 2
and return this value. If number
is odd, then collatz()
should print and return 3 * number + 1
.

Then write a program that lets the user type in an integer and that keeps calling collatz()
on that number until the function returns the value 1
. (Amazingly enough, this sequence actually works for any integer — sooner or later, using this sequence, you’ll arrive at 1! Even mathematicians aren’t sure why. Your program is exploring what’s called the Collatz sequence, sometimes called “the simplest impossible math problem.”)

Remember to convert the return value from input()
to an integer with the int()
function; otherwise, it will be a string value.

Hint: An integer number
is even if number % 2 == 0
, and it’s odd if number % 2 == 1
.

The output of this program could look something like this:

Enter number:
3
10
5
16
8
4
2
1
'''

# TODO: make algorithm work.

def collatz(number):
    while number > 1:
        if number % 2 == 0:
            return number // 2
        elif number % 2 == 1:
            return 3 * number + 1



data = int(input("Enter number: "))

try:
    collatz(data)
except ValueError as er:
    print("Please enter an integer.")
