Let’s make it a one liner :D
fib = Hash.new {|hash, key| hash[key] = key < 2 ? key : hash[key-1] + hash[key-2] }
Example: fib[123] # => 22698374052006863956975682
Makes use of memoization.
fib = Hash.new {|hash, key| hash[key] = key < 2 ? key : hash[key-1] + hash[key-2] }
Example: fib[123] # => 22698374052006863956975682
Makes use of memoization.
fib = Hash.new do |k, v|
next 1 if v == 0 || v == 1
k[v] = k[v-1] + k[v-2]
end