cokofreedom
1/11/2008 9:06:00 AM
On Jan 11, 9:46 am, Gary Herron <gher...@islandtraining.com> wrote:
> Tom_chicollegeboy wrote:
> > here is what I have to do:
>
> > This question involves a game with teddy bears. The game starts when I
> > give you some bears. You then start giving me back some bears, but you
> > must follow these rules (where n is the number of bears that you
> > have):
>
> This sounds very much like a homework assignment, and so should probably
> not be answered here. (Neither should it have been asked here.) If,
> in your attempt to write this program, you have some questions about
> Python, then I encourage to ask those questions here.
>
> Gary Herron
>
> > If n is even, then you may give back exactly n/2 bears. (Hint: To test
> > whether n is even, use the expression ((n % 2) == 0).)
> > If n is divisible by 3 or 4, then you may multiply the last two digits
> > of n and give back this many bears. (By the way, the last digit of n
> > is n%10, and the next-to-last digit is (n%100)/10; this rule may not
> > be used if either of the last two digits is 0.)
>
> > If n is divisible by 5, then you may give back exactly 42 bears.
> > The goal of the game for you is to end up with EXACTLY 42 bears.
>
> > For example, suppose that you start with 250 bears. Then you could
> > make these moves:
>
> > Start with 250 bears.
> > Since 250 is divisible by 5, you may return 42 of the bears, leaving
> > you with 208 bears.
> > Since 208 is even, you may return half of the bears, leaving you with
> > 104 bears.
> > Since 104 is even, you may return half of the bears, leaving you with
> > 52 bears.
> > Since 52 is divisible by 4, you may multiply the last two digits
> > (resulting in 10) and return these 10 bears. This leaves you with 42
> > bears.
> > You have reached the goal!
> > Now, you are to write a program that, if I give you n bears, returns
> > true if it is at all possible for you to win the game. Your program
> > must use recursion to check all possible ways in which you can apply
> > the rules.
>
> > Usage:
>
> >>>> bears(42)
>
> > True
>
> >>>> bears(250)
>
> > True
>
> >>>> bears(50)
>
> > False
>
> >>>> bears(84)
>
> > True
>
> >>>> bears(41)
>
> > False
>
> > As you see my program must use recursion.
>
> > I came up with this idea but I am not sure if its right or are there
> > any minor errors that I can easily fix:
>
> > def bears (n):
> > if n==42:
> > return True
> > if n%5==0:
> > bears(n-42)
> > if n%2==0:
> > bears(n/2)
> > if n%3==0 or n%4==0:
> > one = (n%10)
> > two = ((n%100)/10)
> > if one!=0 and two!=0:
> > bears(n-(one*two))
> > return False
>
> > If a game hits 42 it should return True, otherwise False. If program
> > never hits 42 and return True, then it returns False. I figured out
> > base case, but I still get False when I enter bears(250). Any help
> > would be very appreciated!
Note that for ;
if one!=0 and two!=0:
you can use
if one and two:
which is my pythonic.
Also in your example with 52, shouldn't it divide by even first?
Obviously this must not happen, thus maybe you should run a check that
when you are returning a new value it does not go below 42? Frankly
this looks like a terrible way to use recursion.