Ruby Fibonacci algorithm

Question

The following is a method I wrote to calculate a value in the Fibonacci sequence:

def fib(n)

    if n == 0
        return 0
    end
    if n == 1
        re         


        

Answer 1

I tried comparing the run time of two fibonacci methods on repl.it

require 'benchmark'

def fib_memo(n, memo = {})
  if n == 0 || n == 1
    return n
  end
  memo[n] ||= fib_memo(n-1, memo) + fib_memo(n-2, memo)
end


def fib_naive(n)
  if n == 0 || n == 1
    return n
  end
  fib_naive(n-1) + fib_naive(n-2)
end

def time(&block) 
  puts Benchmark.measure(&block) 
end

time {fib_memo(14)}
time {fib_naive(14)}

Output

0.000000   0.000000   0.000000 (  0.000008)
0.000000   0.000000   0.000000 (  0.000099)

As you can see, the runtime is quite different. As @Uri Agassi suggested, use memoization. The concept is explained quite well here https://stackoverflow.com/a/1988826/5256509