W1/3 - Time Conversion (elixir) (#141)

The third challenge of week one.

Another one off #117 

Closes #124

Author: jamiecurle

mix.exs

@@ -1,4 +1,4 @@
-defmodule Hackerank.MixProject do
+defmodule HackerRank.MixProject do
   use Mix.Project
 
   @doc """

test/test_helper.exs

@@ -1,4 +1,4 @@
-defmodule Hackerrank.Test.Helper do
+defmodule HackerRank.Test.Helper do
   @moduledoc """
   A set of utilities for testing the Elixir HackerRank challenges
   """

w1/mini_max_sum.ex

@@ -1,4 +1,4 @@
-defmodule  Hackerrank.W1.MiniMaxSum do
+defmodule  HackerRank.W1.MiniMaxSum do
   @moduledoc """
   Mini Max Sum – Challenge 2 – Week 1
   <https://www.hackerrank.com/challenges/three-month-preparation-kit-mini-max-sum/problem>

w1/mini_max_sum_test.exs

@@ -1,8 +1,8 @@
-defmodule Hackerank.W1.MiniMaxSumTests do
+defmodule HackerRank.W1.MiniMaxSumTests do
 
   use ExUnit.Case
-  alias Hackerrank.Test.Helper
-  alias Hackerrank.W1.MiniMaxSum
+  alias HackerRank.Test.Helper
+  alias HackerRank.W1.MiniMaxSum
 
   @pattern "w1/tc/2_*.txt"
 

w1/plus_minus.ex

@@ -1,4 +1,4 @@
-defmodule Hackerrank.W1.PlusMinus do
+defmodule HackerRank.W1.PlusMinus do
   @doc """
   The challenge function.
   """

w1/plus_minus.go

@@ -44,7 +44,7 @@ func PlusMinus(arr []int32) [3]string {
 	solution[1] = fmt.Sprintf("%.6f", n_ratio)
 	solution[2] = fmt.Sprintf("%.6f", z_ratio)
 
-	// Hackerank wants you to print them
+	// HackerRank wants you to print them
 	for _, value := range solution {
 		fmt.Println(value)
 	}

w1/plus_minus_test.exs

@@ -1,8 +1,8 @@
-defmodule Hackerank.W1.PlusMinusTest do
+defmodule HackerRank.W1.PlusMinusTest do
 
   use ExUnit.Case
-  alias Hackerrank.Test.Helper
-  alias Hackerrank.W1.PlusMinus
+  alias HackerRank.Test.Helper
+  alias HackerRank.W1.PlusMinus
 
   @pattern "w1/tc/1_*.txt"
 

w1/time_conversion.ex

@@ -0,0 +1,46 @@
+defmodule HackerRank.W1.TimeConversion do
+  @moduledoc """
+  Time Conversion – Challenge 3 – Week 1
+  <https://www.hackerrank.com/challenges/three-month-preparation-kit-time-conversion/problem>
+  """
+
+  @doc """
+  Converts 12-hour AM/PM time format to 24-hour military time.
+
+  ## Examples
+
+      iex> challenge("07:05:45PM")
+      "19:05:45"
+
+  ## Constraints
+
+  - Input format: `"hh:mm:ssAM"` or `"hh:mm:ssPM"`
+  - Always returns a string in 24-hour format
+  """
+  @spec challenge(String.t()) :: String.t()
+  def challenge(s) do
+    # Dates / Times are not Elixis strong suit
+    # However, binary string pattern matching is so let's do that then
+    [hh, mm, ss_am_pm] = String.split(s, ":")
+
+    # now we need am / pm
+    <<ss::binary-size(2), period::binary>> = ss_am_pm
+
+    # now parse into the correct types
+    hour = parse_hour(hh, period)
+    minute = String.to_integer(mm)
+    second = String.to_integer(ss)
+
+    # run everything through pad and return with Enum.map_join
+    Enum.map_join([hour, minute, second], ":", &pad2/1)
+    end
+
+  defp parse_hour("12", "AM"), do: 0
+  defp parse_hour(h, "AM"), do: String.to_integer(h)
+  defp parse_hour("12", "PM"), do: 12
+  defp parse_hour(h, "PM"), do: String.to_integer(h) + 12
+
+  defp pad2(number) do
+    :io_lib.format("~2..0B", [number]) |> to_string()
+  end
+end

w1/time_conversion_test.exs

@@ -0,0 +1,18 @@
+defmodule HackerRank.W1.TimeConversionTests do
+  use ExUnit.Case
+  alias HackerRank.Test.Helper
+  alias HackerRank.W1.TimeConversion
+
+  @pattern ~w"w1/tc/3_*.txt"
+
+  test "run the tests" do
+    Helper.test_all(@pattern, &parse_args/1, &parse_expected/1 )
+    |> Enum.each(fn [args, expected] ->
+      assert TimeConversion.challenge(args) == expected
+    end)
+  end
+
+  def parse_args([raw]), do: raw
+  def parse_expected([raw]), do: raw
+
+end