Problem 2

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, …

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

Solution

#By considering the terms in the Fibonacci sequence

#whose values do not exceed four million, find the

#sum of the even valued terms.

# this uses the same technique

# as the c# implementation

# I find this initialization

# syntax interesting

answer = 0

fib0, fib1, fib2 = 1, 1, 2;

while fib2 < 4000000

    answer += fib2

    #odd + even = odd

    fib0 = fib1 + fib2;

    #odd + even = odd

    fib1 = fib0 + fib2;

    #odd + odd = even

    fib2 = fib0 + fib1;

end

puts answer

Discussion

This is obviously a port of the C# solution.  The one piece I find interesting is

fib0, fib1, fib2 = 1,1,2;

Seems to be equivalent to

fib0 = 1, fib1 = 1, fib2 = 2;

For cutting and pasting large lists, the first option might be more attractive?  Why not use an array in that case?  I suppose I’ll learn more as I continue down the path.

If you have questions, leave a comment or please find me on Twitter (@azzlsoft) or email (rich@azzlsoft.com).