Fibonacci Sequence Generator with Dynamic Programming

fib.rb

require 'benchmark'

def fib(n)
  raise ArgumentError, "needs to be positive! n: #{n}" if n < 0
  Array.new(n, 1).tap do |seq|
    (2..seq.length-1).each do |idx|
      seq[idx] = seq[idx-1] + seq[idx-2]
    end if n > 2
  end
end


(0..10).each do |i|
  puts fib(i).inspect
end

begin
  fib(-1)
rescue => e
  puts e.inspect
end

# # puts fib(100000).inject(&:+)
puts Benchmark.realtime{ fib(200000).inject(&:+) }