ranges_overlap_sum.rb

#  You’re given two integer ranges (x1, x2) and (y1, y2). For example, the ranges (1, 10) and (5, 20). Sum the
#  numbers that exist in both ranges. In our example, we would add up 5, 6, 7, 8, 9 and 10 (for a total of 45) since
#  5, 6, 7, 8, 9 and 10 exist in both ranges.

#The function should look like this (in Ruby):

def sum_of_intersection(x1, x2, y1, y2)
  intersection = (x1..x2).to_a & (y1..y2).to_a
  intersection.inject { |sum, i| sum + i }
end

puts sum_of_intersection(1,10,5,20)