# Day 13 of 30 Ruby Coding Challenge - Fibonacci Sequence in Ruby

# Day 13 of 30 Ruby Coding Challenge - Fibonacci Sequence in Ruby

### Day 13 of 30. We're going to solve the famous Fibonacci sequence in Ruby. The next videos are going to be all about getting the algorithm better

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

## Fancy Fibonacci Algorithm Definition

- To get the next number in a sequence, you have to sum the previous two numbers.

One important point: The Fibonacci sequence already **starts** with **0** and **1** as the first **2 numbers**

Here is a sequence to help you out a bit more:

`0 1 1 2 3 5 8 13 21 34 55 88 ...`

Perfect. Now we want to solve the following puzzle:

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

**First Real Example:**

I want to calculate the first 8 numbers in a Fibonacci sequence:

`xxxxxxxxxx`

`0 1 1 2 3 5 8 13`

**Second Real Example:**

I want to calculate the first 10 numbers in a Fibonacci sequence:

`xxxxxxxxxx`

`0 1 1 2 3 5 8 13 21 34`

I’m pretty sure you got it : )

## Fibonacci Algorithm in Ruby

**Step 1**

- let’s create the
**fibonacci()**method - then we’ll start the sequence with 0 and 1

`xxxxxxxxxx`

`def fibonacci(count)`

` n1 = 0`

` n2 = 1`

` sequence = [n1, n2]`

`end`

`puts fibonacci(8)`

**Step 2**

- because the list starts with 2 numbers, we can calculate the next one using a
**while loop**

`xxxxxxxxxx`

`def fibonacci(count)`

` n1 = 0`

` n2 = 1`

` sequence = [n1, n2]`

` while count > 2 # just a while loop expression that decrements the argument count`

` count = count - 1`

` end`

` return sequence`

`end`

`puts fibonacci(8)`

`# 0 1 1 2 3 5 8 13`

**Step 3**

- the
**next number**is the**sum**of the**previous 2**numbers

`xxxxxxxxxx`

`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`

Pretty simple, isn’t it?

Although the code is simple, it’s far from a good code design because:

- it lacks readability
- it updates an argument received in the method
- it has too many local variables

To be honest, sometimes (and even most of the time), a good code design is a matter of context and personal taste, and maybe you might think that this code is already good enough, and I don’t blame you. However, I’ll solve the same problem using a different approach that probably you might like better

Hope to see you in the next Ruby Coding Challenge : )

Don’t forget to come by and say hi Alex

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Published at DZone with permission of Alexandre Gama . See the original article here.

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