I have a method called fibs_rec that results in an unexpected output:
def fibs_rec(n)
if n == 1 || n == 0
return 1
else
a = fibs_rec(n-1) + fibs_rec(n-2)
puts a
return a
end
end
fibs_rec(5)
The call fibs_rec(5) should return 1,1,2,3,5 but here is the actual output:
2
3
2
5
2
3
8
Not only is the output incorrect, it lacks a number from the beginning.
Can someone explain why is this happening?
This is correct since your recursion is splitting into two sub-problems every time it recurses. If you want the series to appear properly then you should try doing this via dynamic programming for O(n) time complexity. As is, the first and second position won’t be printed because of the base case in the recursion.
As for the incorrect answer, it seems you have not accounted for the sequence starting with 0 index. Either find 4 index in the function which will give the fifth element or modify your function to work with position instead of index.
-1 the element needed in the series.
1,1,2,3,5seems like multiple values. You could return the values as an array, i.e.[1,1,2,3,5]. Or – a bit more idiomatic – you couldyieldeach value to a block. (maybe returning an enumerator if no block is given)putsonly if n > 1, and only for the case n <= 1, fib_rec would return a 1. Hence you never see a 1 in your output. Also, your question is unclear: You are asking about the output of the function, which is whatputsis taken care, but then are also mention return a value. Outputting something and returning a value are two different, unrelated things, so please make clear in your posting what you exactly want.