Class: Integer

Inherits:
Object
  • Object
show all
Defined in:
lib/binomial/integer.rb

Overview

Integer extension to add choose function

Instance Method Summary collapse

Instance Method Details

#choose(k) ⇒ Object

binomial coefficient: n C k



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# File 'lib/binomial/integer.rb', line 4

def choose(k)
  # n!/(n-k)!
  top = (self-k+1..self).inject(1, &:*) 
  # k!
  bottom = (2..k).inject(1, &:*)
  top / bottom
end