Даяна обнови решението на 26.10.2015 11:31 (преди над 8 години)
+class PrimeSequence
+ include Enumerable
+
+ attr_reader :limit
+
+ def initialize(limit)
+ @limit = limit
+ end
+
+ def to_a
+ enum_for(:each_number).lazy.select{ |x| prime?(x) }.take(@limit).to_a
+ end
+
+ private
+
+ def each_number
+ n = 0
+ loop do
+ n += 1
+ yield n
+ end
+ end
+
+ def prime?(n)
+ return false if n < 2
+ (2..n/2).none? {|i| n % i == 0}
+ end
+end
+
+class RationalSequence
+ include Enumerable
+
+ def initialize(limit)
+ @limit = limit
+ @k = []
+ @s = collect_numbers
+ end
+
+ def to_a
+ @k.take(@limit)
+ end
+
+ def collect_numbers
+ n = Rational(1)
+ @k << n
+ while @k.size < @limit
+ n = denominator(n) if n.denominator == 1
+ n = numerator(n) if n.numerator == 1
+ end
+ end
+
+ def numerator(n)
+ n = Rational(n.numerator, n.denominator + 1)
+ @k << n
+ target = n.denominator
+ while n.numerator < target
+ n = next_rational_numerator(n.numerator, n.denominator)
+ @k << n
+ end
+ n
+ end
+
+ def denominator(n)
+ n = Rational(n.numerator + 1, n.denominator)
+ @k << n
+ target = n.numerator
+ while n.denominator < target
+ n = next_rational_denominator(n.numerator, n.denominator)
+ @k << n
+ end
+ n
+ end
+
+ def next_rational_denominator(n_numerator, n_denominator)
+ i = 1
+ while @k.include?(Rational(n_numerator-i, n_denominator+i))
+ i += 1
+ end
+ Rational(n_numerator-i, n_denominator+i)
+ end
+
+ def next_rational_numerator(n_numerator, n_denominator)
+ i = 1
+ while @k.include?(Rational(n_numerator+i, n_denominator-i))
+ i += 1
+ end
+ Rational(n_numerator+i, n_denominator-i)
+ end
+end
+
+class FibonacciSequence
+ include Enumerable
+
+ attr_reader :limit
+
+ def initialize(limit, initial_values= {first: 1, second: 1})
+ @limit = limit
+ @initial_values = initial_values
+ end
+
+ def to_a
+ enum_for(:each_number).lazy.take(@limit).to_a
+ end
+
+ private
+
+ def each_number
+ b, a = @initial_values[:first], @initial_values[:second]
+ loop do
+ yield b
+ a, b = a + b, a
+ end
+ end
+end
+
+module DrunkenMathematician
+ module_function
+
+ def meaningless(n)
+ first_n = RationalSequence.new(n).to_a
+ second_group = second_group(first_n)
+ first_group = first_n - second_group
+ product(first_group) / product(second_group)
+ end
+
+ def aimless(n)
+ first_n = PrimeSequence.new(n).to_a
+ array_rationals = make_pairs(first_n).map {|x| Rational(x[0], x[1])}
+ sum_rationals(array_rationals)
+ end
+
+ def worthless(n)
+ fibonacci_n = FibonacciSequence.new(n).to_a.last
+ first_n_rationals = RationalSequence.new(n).to_a
+ biggest_slice(fibonacci_n, first_n_rationals)
+ end
+
+ def sum_rationals(rationals)
+ rationals.reduce{|sum, x| sum + x}
+ end
+
+ def biggest_slice(number, rationals)
+ while sum_rationals(rationals) > number
+ rationals = rationals - [rationals.last]
+ end
+ rationals
+ end
+
+ def split(first_n, equal_to)
+ s = []
+ first_n.each_index {|x| s << first_n[x] if x % 2 == equal_to }
+ s
+ end
+
+ def make_pairs(first_n)
+ first_group = split(first_n, 0)
+ second_group = split(first_n, 1)
+ first_group.zip(second_group)
+ end
+
+ def product(group)
+ group.reduce{|sum, x| sum * x}
+ end
+
+ def second_group(first_n)
+ first_n.select { |x| !prime?(x.numerator) && !prime?(x.denominator) }
+ end
+
+ def prime?(n)
+ return false if n < 2
+ (2..n/2).none? {|i| n % i == 0}
+ end
+end