Project Euler [SPOILER #3]

Geoff Canyon Rev gcanyon+rev at gmail.com
Thu Feb 25 09:21:48 EST 2010


It's hurting my head trying to figure out why yours works. ;-)

That said, it's very slow. The simple brute force method is roughly
100 times faster (since it doesn't iterate 10,000 times but only 100):

      put 0 into total
      put 0 into summer
      repeat with i = 1 to 100
         subtract i^2 from total
         add i to summer
      end repeat
      add summer^2 to total

_That_ said, I believe there is yet a faster way. I believe yours is
O(n^5), mine is O(n^3), but O(n^2) is possible. (If someone
understands big O notation better than I do feel free to jump in here)

gc

On Wed, Feb 24, 2010 at 1:47 PM, Brian Yennie <briany at qldlearning.com> wrote:
> No, we're actually talking about #6 =).
>
> I put them in order of difficulty and this becomes the 3rd one... but it's actually id 6.
>
>> Are we talking about the same #3?
>>
>> The prime factors of 13195 are 5, 7, 13 and 29.
>>
>> What is the largest prime factor of the number 600851475143 ?
>>
>>
>>
>> On Tue, Feb 23, 2010 at 11:04 AM, Brian Yennie <briany at qldlearning.com> wrote:
>>> I'm pretty proud of this one for #3... SPOILER ALERT SPOILER ALERT... scroll down if you want to see. Great site find, Andre!!
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>>> put 0 into total
>>> repeat with i=1 to 100
>>> repeat with j=1 to 100
>>>    if (i=j) then next repeat
>>>    add i*j to total
>>> end repeat
>>> end repeat
>>>
>>> _____
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