Memoization in ruby

fibo_ruby.rb

require 'rubygems'
require 'benchmark'

def fibonacci(n)
  return n if n <= 1
  fibonacci( n - 1 ) + fibonacci( n - 2 )
end

@cache = [0,1]
def fibo(n)
  return @cache[n] if @cache[n]
  @cache[n] = fibo(n-1) + fibo(n-2)
end

@fibos = Hash.new(0)
def count_fibos(n)
  @fibos[n] = @fibos[n] + 1
  return n if n <= 1
  count_fibos( n - 1 ) + count_fibos( n - 2 )
end

puts Benchmark.measure {
    puts fibonacci(1)
}

puts Benchmark.measure {
    puts fibo(1)
}

count_fibos(5)
p @fibos