[Elixir]implement binary search with Elixir

	defmodule Search do
	def binary(_, []), do: -1
	def binary(search, [head\|tail]) when tail == [], do: if search == head, do: 0, else: -1
	def binary(search, list), do: binary search, 0, length(list) – 1, list

	defp binary(search, left_len, right_len, list) when right_len – left_len == 1 do
	cond do
	Enum.at(list, left_len) == search ->
	left_len
	Enum.at(list, right_len) == search ->
	right_len
	true ->
	-1
	end
	end

	defp binary(search, left_len, right_len, list) do
	mid = round((right_len – left_len) / 2)
	cond do
	Enum.at(list, mid) > search ->
	binary search, left_len, mid, list
	true ->
	binary search, mid, right_len, list
	end
	end
	end

	ExUnit.start

	defmodule SearchTest do
	use ExUnit.Case

	test "empty case" do
	assert Search.binary(1, []) == -1
	end

	test "one case" do
	assert Search.binary(1, [1]) == 0
	assert Search.binary(2, [1]) == -1
	end

	test "two case" do
	assert Search.binary(1, [1, 2]) == 0
	assert Search.binary(2, [1, 2]) == 1
	assert Search.binary(3, [1, 2]) == -1
	end

	test "many case" do
	assert Search.binary(1, [1, 2, 5]) == 0
	assert Search.binary(5, [1, 2, 5]) == 2
	assert Search.binary(3, [1, 2, 5]) == -1
	end
	end

Published by KazuCocoa