Question

I am writing a method that returns the nth element in the Fibonacci sequence, but am running into an unexpected end error.

def fib_seq(n)

  a = [0]

  n.times do |i|
    if i==0
      a[i] = 0
    else if i==1
      a[i] = 1
    else
      a[i] = a[i-1] + a[i-2]
    end  
  end

  return a[n]
end

puts fib_seq(4)

Any tip on what I can be screwing up on?

Answer 1

Assuming you are trying to return the nth (and not the (n-1)th, i.e. fib(1) = 0 NOT fib(0) = 0).

I fixed it by changing:

else if i==1

to

elsif i==1

(AND)

return a[n]

to

return a[n - 1]

So your final code should look like:

def fibSeq(n)

  a = [0]

  n.times do |i|
    if i==0
      a[i] = 0
    elsif i==1
      a[i] = 1
    else
      a[i] = a[i-1] + a[i-2]
    end  
  end

  return a[n-1]
end

puts fibSeq(4)

Per your comment below, the following code will work:

def fibSeq(n)

  a = [0]

  (n+1).times do |i|
    if i==0
      a[i] = 0
    elsif i==1
      a[i] = 1
    else
      a[i] = a[i-1] + a[i-2]
    end  
  end

  return a[n]
end

puts fibSeq(4)

If you want to output the fibs as a list then use:

return a[0..n]

Instead of

return a[n]