mergesort

mergesort.ex

defmodule People do
  @people ["Mary","John","Emma"]
  @heights [180,165,170]

  def sort_heights(names, heights) do
    heights
    |> Enum.zip(names)
    |> mergesort()
    |> Enum.unzip()
    |> elem(1)
  end

  def merge([], ys), do: ys
  def merge(xs, []), do: xs
  def merge([x | xs] = l1, [y | ys] = l2) do
    if x >= y do
      [x | merge(xs, l2)]
    else
      [y | merge(l1, ys)]
    end
  end

  def mergesort(xs) do
    n = length(xs)
    if n == 1 do
      xs
    else
      {xs, ys} = Enum.split(xs, div(n, 2))
      merge(mergesort(xs), mergesort(ys))
    end
  end
end