> Any brute force solution will be relatively slow. The fast solutions
> require a doing math to simplify.
Quite right. The fault lies with me rather than with Clojure. I'll rework
the code so that it expands to:
2^4 * 3^2 * 5^1 * 7^1 * 11^1 * 13^1 * 17^1 * 19^1
Relevant Stack Overflow post:
http://stackoverflow.com/questions/14668272/what-can-i-do-to-speed-up-this-code
On Tuesday, October 1, 2013 11:56:48 AM UTC-7, Ben wrote:
>
> You can actually solve this problem quite directly. I just looked up my
> python solution and it's just "print 9*16*5*7*11*13*17*19".
>
>
> On Tue, Oct 1, 2013 at 11:22 AM, David Chambers
> <[email protected]<javascript:>
> > wrote:
>
>> Last night I attempted Project Euler #5<http://projecteuler.net/problem=5>in
>> Clojure. The problem is as follows:
>>
>> > # Smallest multiple
>> >
>> > 2520 is the smallest number that can be divided by each of the numbers
>> > from 1 to 10 without any remainder.
>> >
>> > What is the smallest positive number that is evenly divisible by all of
>> the
>> > numbers from 1 to 20?
>>
>> Here's my solution:
>>
>> (defn divisible?
>> [numer denom]
>> (= 0 (mod numer denom)))
>>
>> (defn smallest-multiple
>> "Find the smallest positive number that is evenly divisible by all
>> of the numbers from 1 to n."
>> [n]
>> (let [s (range 1 (inc n))]
>> (first (filter (fn [x] (every? (partial divisible? x) s))
>> (rest (range))))))
>>
>> This gives the expected answer for *n* of 10, but takes a long time to
>> solve *n* of 20. I'd like to understand what make this code slow. Am I
>> doing something inefficiently? What steps might I take to rework this
>> code to have it solve *n* of 20 within a minute?
>>
>> ---
>>
>> p.s. I'm new to Clojure. Don't hesitate to mention applicable Clojure
>> idioms of which I may not be aware.
>>
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>
>
>
> --
> Ben Wolfson
> "Human kind has used its intelligence to vary the flavour of drinks, which
> may be sweet, aromatic, fermented or spirit-based. ... Family and social
> life also offer numerous other occasions to consume drinks for pleasure."
> [Larousse, "Drink" entry]
>
>
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