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Discussion on: Daily Challenge #7 - Factorial Decomposition

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Replies for: Woo 3 days in a row! I'm not too good when it comes to maths and I'm sure there are loads of more efficient algorithms for finding prime factors, ...

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spaciecat profile image
Spacie • • Edited

Turns out there's actually a built in method for this ... So just the formatting I guess...

require 'prime'
def decomp n
  fact = Math.gamma(n + 1).to_i
  "n = #{n}; n! = #{fact}; decomp(n!) = #{n == 1 ? "1" : Prime.prime_division(fact).map(&proc {|pair| pair[1] > 1 ? "#{pair[0]}^#{pair[1]}" : pair[0]}).join(" * ")}"
end
(1..10).each {|x| puts decomp x}