Help with Python

ViewSonic20061 · #1 (**permalink**) 11-02-2007, 07:00 AM

Does anyone know how to make the program running until the ouput becomes 1? If hail(x) = x/2 if x is even(i.e., x%2 is 0) and hail(x) = 3x+1 if x is odd(i.e., x%2 is 1)

example:
Please enter a starting value: 3
Output will be:
3
10
5
16
8
4
2
1

so far wat i came up with was:

Code:

x =  int(raw_input("Please enter a starting value:"))

def hail(x):
    if x % 2 == 0:
        return x / 2
    else:
        return (3*x)+1
output = hail(x)
print output

but i still cant seem to think of a way to make them repeat itself and keep caculating till it becomes one. Any ideas or suggestions?

HelloWorld · #2 (**permalink**) 11-02-2007, 07:16 PM

Sorry I'm unfamiliar with Python, but if you've the function already...

Quote:

hail(x) = x/2

and

Quote:

hail(x) = 3x+1

Then write something like:

Pseudo code:

Code:

Integer Function hailEven(Integer x)
     return x/2
End Function hailEven

Integer Function hailOdd(Integer x)
     return 3x+1
End Function hailOdd

Main method
    Integer Command
    Do
        Show.Output("Enter integer (-1 to exit): ")
        Command = Get.InputStream
        If Command % 2 = 0 // This is even
           hailEven(Command)
        Else // Odd
           hailOdd(Command)
        End If
    While (Command is not -1)
End Main

I hope that helps

writtinfool · #3 (**permalink**) 11-03-2007, 02:28 AM

"""
Here's a solution that uses a bastardized "do while" loop(without out the do)
and recursion. you need the recursion to reprocess the result.
do while loops have been considered unpythonic, although that attitude that is changing
"""

Code:

x = int(raw_input("Please enter a starting value:"))

def hail(x):
    if x % 2 == 0:
        return x / 2
    else:
        return (3*x)+1

while True:
    x = hail(x)    # recursive function call
    output = x  # don't really need the extra variable but it makes things clearer
    print output
    if output == 1:
        break

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The Following 2 Users Say Thank You to writtinfool For This Useful Post:
HelloWorld (11-03-2007), TeraTask (11-03-2007)