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| class PrimeFactor | |
| attr_accessor :all_factors | |
| def largest_divisor_less_than(number) | |
| divisor = 2 | |
| while divisor <= Math.sqrt(number) | |
| return number / divisor if number % divisor == 0 | |
| divisor = divisor + 1 | |
| end | |
| return 1 | |
| end | |
| def initialize | |
| self.all_factors = Hash.new do |h, index| | |
| number = index | |
| divisor = largest_divisor_less_than(number) | |
| if divisor == 1 | |
| factors = [] | |
| factors << number if number > 1 | |
| h[index] = factors | |
| else | |
| number = number / divisor | |
| h[index] = [number] + h[divisor] | |
| end | |
| end | |
| end | |
| def [](number) | |
| all_factors[number] | |
| end | |
| end | |
| describe PrimeFactor do | |
| factor = PrimeFactor.new | |
| { 1 => [], | |
| 2 => [2], | |
| 3 => [3], | |
| 4 => [2, 2], | |
| 5 => [5], | |
| 6 => [2, 3], | |
| 8 => [2, 2, 2], | |
| 12 => [2,2,3], | |
| 16 => [2, 2, 2, 2], | |
| 18 => [2, 3, 3], | |
| 24 => [2, 2, 2, 3], | |
| (2*2*3*3) => [2, 2, 3, 3], | |
| (2*3*3*5*5*5*11*17) => [2, 3, 3, 5, 5, 5, 11, 17] | |
| }.each do |number, factors| | |
| example("#{number} => #{factors.inspect}") { factor[number].should == factors } | |
| end | |
| end |
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Nice working around inheritance.