欧拉计划第二题

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.
翻译下：就是在斐波那契数列中找到小于4000000的那个数，然后求它之前的所有偶数的和并打印出来
even-valued terms 偶数
odd-valued terms 奇数
Ruby代码：

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def 
  firstNum,secondNum = 0, 1
  sumNum = 0

  while secondNum < 4000000
    firstNum, secondNum = secondNum, firstNum + secondNum

    sumNum += secondNum if secondNum % 2 ==0
  end
  puts "The sum of all even-valued is #{sumNum}"
end
fabonacci()

输出结果：

1

The sum of all even-valued is 4613732