Velocity Reviews > Sum of the factorial of the digits of a number - wierd behaviour

# Sum of the factorial of the digits of a number - wierd behaviour

SiWi
Guest
Posts: n/a

 12-09-2009
Dear python community,
I've got a wierd problem and I hope you can help me out at it.
I wrote the following code to find the Sum of the factorial of the
digits of a number (this is for Project Euler 74):

def fac(n):
x=1
for i in range(2,n+1):
x*=i
return x

t=tuple(fac(n) for n in range(1,10))

def decimals(x):
i=1
d=[]
while x>0:
d.append(x%10)
x=x/10
return d

def sumfac(x):
return sum(t[n-1] for n in decimals(x))

The problem is that i get the following results, for which I can't see
any reason:
sumfac(145)->145 (1!+4!+5!=1 + 24 +120 = 145) - ok
sumfac(1454)-> 169 - ok
sumfac(45362) -> 872 - ok
sumfac(363600) -> 727212 - wrong, should be1454

Greetings,
SiWi.

SiWi
Guest
Posts: n/a

 12-09-2009
On Dec 9, 6:36*pm, SiWi <(E-Mail Removed)> wrote:
> Dear python community,
> I've got a wierd problem and I hope you can help me out at it.
> I wrote the following code to find the Sum of the factorial of the
> digits of a number (this is for Project Euler 74):
>
> def fac(n):
> * * x=1
> * * for i in range(2,n+1):
> * * * * x*=i
> * * return x
>
> t=tuple(fac(n) for n in range(1,10))
>
> def decimals(x):
> * * i=1
> * * d=[]
> * * while x>0:
> * * * * d.append(x%10)
> * * * * x=x/10
> * * return d
>
> def sumfac(x):
> * * return sum(t[n-1] for n in decimals(x))
>
> The problem is that i get the following results, for which I can't see
> any reason:
> sumfac(145)->145 (1!+4!+5!=1 + 24 +120 = 145) - ok
> sumfac(1454)-> 169 - ok
> sumfac(45362) -> 872 - ok
> sumfac(363600) -> 727212 - wrong, should be1454
>
> Greetings,
> SiWi.

Oops, found it myself. You can ignote the message above.

Jon Clements
Guest
Posts: n/a

 12-09-2009
Even though you've worked it out -- a couple of tips:

On Dec 9, 5:39*pm, SiWi <(E-Mail Removed)> wrote:
> On Dec 9, 6:36*pm, SiWi <(E-Mail Removed)> wrote:
>
>
>
> > Dear python community,
> > I've got a wierd problem and I hope you can help me out at it.
> > I wrote the following code to find the Sum of the factorial of the
> > digits of a number (this is for Project Euler 74):

>
> > def fac(n):
> > * * x=1
> > * * for i in range(2,n+1):
> > * * * * x*=i
> > * * return x

>

numpy/scipy etc... are quite useful for Euler

They contain a function to do factorials (and loads more).

This to one of the readable uses of 'reduce':
def fac(n):
reduce(operator.mul, xrange(2, n+1), n)

> > t=tuple(fac(n) for n in range(1,10))

>
> > def decimals(x):
> > * * i=1
> > * * d=[]
> > * * while x>0:
> > * * * * d.append(x%10)
> > * * * * x=x/10
> > * * return d

The builtin str object can take integers and return it as a string.

def decimals(x):
return map(int, str(x))
decimals(145) == [1, 4, 5]

>
> > def sumfac(x):
> > * * return sum(t[n-1] for n in decimals(x))

>

And join the two:
print sum(fac(n) for n in decimals(145))

> > The problem is that i get the following results, for which I can't see
> > any reason:
> > sumfac(145)->145 (1!+4!+5!=1 + 24 +120 = 145) - ok
> > sumfac(1454)-> 169 - ok
> > sumfac(45362) -> 872 - ok
> > sumfac(363600) -> 727212 - wrong, should be1454

>
> > Greetings,
> > SiWi.

>
> Oops, found it myself. You can ignote the message above.

You might also find it useful to write generators (esp. for primes and
factorials).

Cheers,

Jon.

geremy condra
Guest
Posts: n/a

 12-09-2009
> numpy/scipy etc... are quite useful for Euler

I've come to love sympy, personally.

> They contain a function to do factorials (and loads more).

>>> from math import factorial
>>> factorial(5)

120

Geremy Condra