Merge pull request exercism#155 from jimmbraddock/bracket-push

Add bracket-push exercise

Author: parkerl

config.json

@@ -12,6 +12,7 @@
     "list-ops",
     "sublist",
     "anagram",
+    "bracket-push",
     "nucleotide-count",
     "rna-transcription",
     "hamming",

exercises/bracket-push/bracket_push.exs

@@ -0,0 +1,9 @@
+defmodule BracketPush do
+  @doc """
+  Checks that all the brackets and braces in the string are matched correctly, and nested correctly
+  """
+  @spec check_brackets(String.t) :: boolean
+  def check_brackets(str) do
+
+  end
+end

exercises/bracket-push/bracket_push_test.exs

@@ -0,0 +1,65 @@
+if !System.get_env("EXERCISM_TEST_EXAMPLES") do
+  Code.load_file("bracket_push.exs")
+end
+
+ExUnit.start
+ExUnit.configure exclude: :pending, trace: true
+
+defmodule BracketPushTest do
+  use ExUnit.Case
+
+  # @tag :pending
+  test "empty string" do
+    assert BracketPush.check_brackets("")
+  end
+
+  @tag :pending
+  test "appropriate bracketing in a set of brackets" do
+    assert BracketPush.check_brackets("{}")
+  end
+
+  @tag :pending
+  test "unclosed brackets" do
+    refute BracketPush.check_brackets("{{")
+  end
+
+  @tag :pending
+  test "more than one pair of brackets" do
+    assert BracketPush.check_brackets("{}[]")
+  end
+
+  @tag :pending
+  test "brackets are out of order" do
+    refute BracketPush.check_brackets("}{")
+  end
+
+  @tag :pending
+  test "nested brackets" do
+    assert BracketPush.check_brackets("{[()]}")
+  end
+
+  @tag :pending
+  test "unbalanced nested brackets" do
+    refute BracketPush.check_brackets("{[}]")
+  end
+
+  @tag :pending
+  test "bracket closure with deeper nesting" do
+    refute BracketPush.check_brackets("{[)][]}")
+  end
+
+  @tag :pending
+  test "bracket closure in a long string of brackets" do
+    assert BracketPush.check_brackets("{[]([()])}")
+  end
+
+  @tag :pending
+  test "should ignore non-bracket characters" do
+    assert BracketPush.check_brackets("{hello[]([a()])b}c")
+  end
+
+  @tag :pending
+  test "string with newlines" do
+    assert BracketPush.check_brackets("[]\n{()}\n[(({}))]\n")
+  end
+end

exercises/bracket-push/example.exs

@@ -0,0 +1,35 @@
+defmodule BracketPush do
+  @brackets %{
+    "{" => "}",
+    "(" => ")",
+    "[" => "]"
+  }
+
+  @doc """
+  Check that all the brackets and braces in the string are matched correctly, and nested correctly
+  """
+  @spec check_brackets(String.t) :: boolean
+  def check_brackets(str) do
+    str
+    |> String.replace(~r/[^\{\}\[\]\(\)]/, "")
+    |> String.codepoints
+    |> check([])
+  end
+
+  defp check([], []), do: true
+  defp check([], _), do: false
+  defp check([h|t], acc) do
+    cond do
+      Map.has_key?(@brackets, h) ->
+        check(t, [Map.get(@brackets, h) | acc])
+      Enum.empty?(acc) and !Map.has_key?(@brackets, h) ->
+        false
+      h != hd(acc) ->
+        false
+      h == hd(acc) ->
+        check(t, tl(acc))
+      true ->
+        true
+    end
+  end
+end