From: Ruby Newbie <yeshvanthni.m@...>
Date: 2007-09-18T18:48:50+09:00
Subject: Faster Alternatives for Recursion in Ruby -Assignment

I have the following assignment to be done.I have written the recursive
API and a loop based solution but what is the faster alternative for
these two that can figure into that "fastfunk(n)" method. Thanks for
your help in advance.

Funkonacci Numbers:
Define the Funkonacci numbers as follows:
  0  if n < 1
        funk(n) =  1  if n = 1
  funk(n - 1) - (2 × funk(n - 2))  otherwise

Write a method funk(n) that calculates the nth Funkonacci number
recursively. Generate a few Funkonacci numbers.  Now write a second
method, fastfunk(n) that calculates the nth Funkonacci number more
quickly

def funkn(n)
  return 0 if n<=0
  return 1 if n==1
  funkn(n - 1) - (2 * funkn(n - 2))
end
def funknloop(n)
  return 0 if n<=0
  return 1 if n==1
  i1 , i2  = 0,1
  for i in 2...(n+1)
  num = i2 - 2*i1
  i1 ,i2 = i2, num
end
i2
end

puts funkn(10)
puts funknloop(10)
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