From: "W. James" <w_a_x_man@...>
Date: 2009-12-19T10:20:14+09:00
Subject: Re: Question about sum of fibonacci sequene [PROJECT EULER]

Panagiotis Atmatzidis wrote:

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> 
> Dear Sirs,
> 
> Just to improve my programming skills and experience I found amusing
> solving problems like the ones posed by project Euler. Doing so,
> using Ruby is a joy, compared to Objective-C that I've used for the
> same purpose in the past.
> 
> I'm stuck in the second problem though. Here is the issue:
> 
> Each new term in the Fibonacci sequence is generated by adding the
> previous two terms. By starting with 1 and 2, the first 10 terms will
> be:
> 
> 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
> 
> Find the sum of all the even-valued terms in the sequence which do
> not exceed four million.
> 
> I think that my code solves it. Works when I test it to smaller
> fractions, can someone reply if there's something wrong with this
> snippet:  - --------------- # fibonacci
> 
> a = 1
> b = 0
> sum = 0
> while a <= 4000000
>  # get the old value of "a"
>  c = a + b
>  #puts c
>  if (c % 2 != 0)
>   sum = sum + c
>  end
>  b = a
>  a = c
> end
>   
> puts sum
> - ---------------
> 
> Well my result is: 10316618 . I know that the original Fibonacci
> sequence will have a (+1) in the beginning of the loop, but
> (probably) for the sake of convenience is ignored. The system however
> returns a "false error" in both 10316618 and 10316618 + 1.
> 
> Thanks in advanced & best regards 


sum = 0
a,b = 1,1
while a <= 4_000_000
  sum += a if a.even?
  a,b = b,a+b
end

p sum


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