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:
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0 1 1 2 3 5 8 13
Second Real Example:
I want to calculate the first 10 numbers in a Fibonacci sequence:
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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
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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
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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
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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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