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bf4/is_fibonacci.rb

Forked from amitkgupta/is_fibonacci.rb
Created October 22, 2015 03:44
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A very fast, near-constant runtime algorithm for determining whether a given number is Fibonacci, accurate up to numbers with trillions of trillions of digits (or something like that)
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is_fibonacci.rb
def is_fibonacci?(num)
n = (Math.log(num*2.23606797749979 + 0.5) * 2.0780869213681945).floor
num == (1.6180339887**n * 0.4472135954999579).round
end
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