wiggle_sort.rb

def wiggle_sort(ary)
  return ary if ary.length < 2

  ary = ary.sort

  lo_index = 0
  hi_index = ary.length.even? ? (ary.length / 2) : (ary.length / 2) + 1

  new_ary = []

  while true
    new_ary << ary[lo_index] # add the number on the smaller side of the array
    lo_index += 1
    break if hi_index > ary.length - 1
    new_ary << ary[hi_index] # add the number on the smaller side of the array
    hi_index += 1
  end

  new_ary
end

p wiggle_sort([1, 5, 1, 1, 6, 4])
p wiggle_sort([1, 3, 2, 2, 3, 1])