Day 14 of 30 Ruby Coding Challenge - Fibonacci Sequence the Ruby Way

Hey friends!

This is the blog post version of the Youtube video from the 30 Ruby Coding Challenges in 30 Days series

Fibonacci Sequence

It’s time to organize the kitchen and to get a better code design to solve the Fibonacci Sequence, which was the previous coding challenge:

We want to calculate the first N numbers in a Fibonacci sequence

This was the last coding solution:

def fibonacci(count)

  n1 = 0

  n2 = 1

  sequence = [n1, n2]

  while count > 2

        # sum of the previous 2 numbers

    n3 = n1 + n2

    sequence.push(n3)

      # assigning the new numbers to calculate the next number in the sequence

    n1 = n2

    n2 = n3

    count = count - 1

  end

  return sequence

end

puts fibonacci(8)

# 0 1 1 2 3 5 8 13

You can be honest, it's not that great.

The Ruby Way to Solve the Fibonacci Problem

Step 1

Ruby allows us to go from one number to another in a sequence like this:

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(0..10).each do |number|

end

In our example we want to avoid the count mutation (fancy name for change). We can do that by the following code:

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(0..count).each do |number|

end

That’s great because Ruby will automatically iterate over the array

Step 2

A better way to store the number in the sequence would be:

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sequence << number if number <= 1

sequence << sequence[-1] + sequence[-2] if sequence.length >= 2

The complete code, a little bit leaner with a better strategy, would be:

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def fibonacci(count)

  sequence = []  

  (0..count).each do |number|

    sequence << number if number <= 1

    sequence << sequence[-1] + sequence[-2] if sequence.length >= 2

  end

  sequence

end

Fantastic! Ruby deals with the problem really well!

The next coding challenge is solving the same problem recursively, which is usually harder to think about. However, it has an even better syntax. See you there!

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