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simeonwillbanks/permutations.rb

Created June 2, 2011 05:27
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#Ruby #math Calculate Permutations
Raw
permutations.rb
# Permutations without Repetition
#
# n!
# --------
# (n-r)!
def permutations(total)
(total-1).downto(1) do |i|
total = total * i unless i == 0
end
total
end
puts permutations(16) # => 20922789888000
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