I’m trying to implement the following function, but it keeps giving me the stack

Question

Asked: June 10, 20262026-06-10T10:09:09+00:00 2026-06-10T10:09:09+00:00

I’m trying to implement the following function, but it keeps giving me the stack level too deep (SystemStackError) error.

Any ideas what the problem might be ?

def fibonacci( n )
    [ n ] if ( 0..1 ).include? n
    ( fibonacci( n - 1 ) + fibonacci( n - 2 ) ) if n > 1
end

puts fibonacci( 5 )

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Editorial Team · Answer 1 · 2026-06-10T10:09:10+00:00

Try this

def fibonacci( n )
  return  n  if ( 0..1 ).include? n
  ( fibonacci( n - 1 ) + fibonacci( n - 2 ) )
end
puts fibonacci( 5 )
# => 5

check this post too Fibonacci One-Liner

You have now been bombarded with many solutions 🙂

regarding problem in ur solution

you should return n if its 0 or 1

and add last two numbers not last and next

New Modified version

def fibonacci( n )
    return  n  if n <= 1 
    fibonacci( n - 1 ) + fibonacci( n - 2 )
end 
puts fibonacci( 10 )
# => 55

One liner

def fibonacci(n)
   n <= 1 ? n :  fibonacci( n - 1 ) + fibonacci( n - 2 ) 
end
puts fibonacci( 10 )
# => 55

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