problem26.rb

#!/bin/env ruby
require 'benchmark'

<<COMM
A unit fraction contains 1 in the numerator. The decimal representation of the unit fractions with denominators 2 to 10 are given:1/2	= 	0.5
1/3	= 	0.(3)
1/4	= 	0.25
1/5	= 	0.2
1/6	= 	0.1(6)
1/7	= 	0.(142857)
1/8	= 	0.125
1/9	= 	0.(1)
1/10	= 	0.1


Where 0.1(6) means 0.166666..., and has a 1-digit recurring cycle. It can be seen that 1/7 has a 6-digit recurring cycle.

Find the value of d  1000 for which 1/d contains the longest recurring cycle in its decimal fraction part.
COMM

def divide y
  x = 1
  res = []
  n = 0
  xs = []
  while true
    x *= 10
    break if x == 0

    if xs.include?(x)
      res.push "()"
      break
    end
    
    if x > y
      xs.push(x)
      res.push(x / y)
      x = x % y
    end
    n += 1
  end
  n
end

res =  (1..1000).inject({}) {|acc, i| acc[divide(i)] = i; acc }
puts res.keys.max
puts res[res.keys.max]