merge_sorted.rb

def destructive_merge(a,b)
  res = []
  while !a.empty? && !b.empty?
    while !a.empty? && a.first < b.first
      res << a.shift
    end
    a, b = b, a
  end
  res
end

a = 100.times.collect { rand * 100 }.sort
b = 100.times.collect { rand * 100 }.sort

c = destructive_merge(a,b)

require 'pp'
pp c