From: Paul Lutus <nospam@...>
Date: 2006-11-27T05:35:12+09:00
Subject: Re: coding practise

sempsteen wrote:

> Yes that's in my mind too. What i wrote was again a dirty, inefficient
> code. I considered on the way you saw me. Here it is:
> 
> class AmicableNumbers
>   def initialize(max = 1000)
>     @numbers = Hash.new
>     findFriends(max)
>   end
>   def findFriends(max)
>     1.upto(max) do |j|
>       t1, t2 = 1, 1
>       2.upto(j / 2) {|i| t1 += i if j % i == 0}
>       2.upto(t1 / 2) {|i| t2 += i if t1 % i == 0}
>       @numbers.store(t1, t2) if j == t2 && t1 != j
>     end

This is very inefficient compared to creating a hash of all sums of
divisors. You need to realize you are recomputing certain quantities over
and over again.

Maybe you would consider profiling this method and comparing it to the
approach of creating a hash of all the sums.

-- 
Paul Lutus
http://www.arachnoid.com