product sum solve

gistfile1.rb

class Timer  
  def initialize
    ObjectSpace.define_finalizer(self,
      self.method(:finalize).to_proc)
    @start = Time.new
    
  end
 
  def finalize(id)
    p "Time: #{Time.now.to_f - @start.to_f} seconds"
  end
end
 
timer = Timer.new

# program start

class Integer
    def prime?
        return true if self == 2
        2.upto(self/2) do |i|
            return false if self % i == 0
        end
        true
    end
end

Lim = 100

q = (2..Lim).to_a

class Num
    def initialize(n, a, b)
        @n = n
        @a = a
        @b = b
    end
    
    attr :n, :a, :b
    
    def to_s
        "[#{@a}, #{@b}]"
    end
end

peshos = []
sashos = []

q.each do |a|
    a.upto(Lim) do |b|
        peshos << Num.new(a*b, a, b)
        sashos << Num.new(a+b, a, b)
    end
end

#P: I can't find them
peshos.reject! do |p|
    p.a.prime? && p.b.prime?
end

#S: I knew it
sashos.reject! do |s|
    s.n%2 == 0 || (s.n-2).prime?
end

#P: Now i know
peshos.select! do |p|
    sashos.detect { |s| p.a == s.a && p.b == s.b }
end

hp = Hash.new

peshos.each do |p|
    hp[p.n] = hp[p.n] ? 2 : 1
end

peshos.reject! do |p|
    hp[p.n] != 1
end

p peshos.length

#S: now I know, too
sashos.select! do |s|
    peshos.detect { |p| p.a == s.a && p.b == s.b }
end

hs = Hash.new

sashos.each do |s|
    hs[s.n] = hs[s.n] ? 2 : 1
end

sashos.reject! do |s|
    hs[s.n] != 1
end

p peshos.length
p sashos