From 5991d1fab107de392b9ed847e7ae8cef284da08a Mon Sep 17 00:00:00 2001
From: James Walker <walkah@walkah.net>
Date: Sun, 16 Sep 2018 15:09:52 -0400
Subject: [PATCH] ruby - flatten-array

---
 ruby/flatten-array/README.md             | 41 ++++++++++++++++++++++++
 ruby/flatten-array/flatten_array.rb      | 16 +++++++++
 ruby/flatten-array/flatten_array_test.rb | 41 ++++++++++++++++++++++++
 3 files changed, 98 insertions(+)
 create mode 100644 ruby/flatten-array/README.md
 create mode 100644 ruby/flatten-array/flatten_array.rb
 create mode 100644 ruby/flatten-array/flatten_array_test.rb

diff --git a/ruby/flatten-array/README.md b/ruby/flatten-array/README.md
new file mode 100644
index 0000000..3187fd5
--- /dev/null
+++ b/ruby/flatten-array/README.md
@@ -0,0 +1,41 @@
+# Flatten Array
+
+Take a nested list and return a single flattened list with all values except nil/null.
+
+The challenge is to write a function that accepts an arbitrarily-deep nested list-like structure and returns a flattened structure without any nil/null values.
+
+For Example
+
+input: [1,[2,3,null,4],[null],5]
+
+output: [1,2,3,4,5]
+
+* * * *
+
+For installation and learning resources, refer to the
+[exercism help page](http://exercism.io/languages/ruby).
+
+For running the tests provided, you will need the Minitest gem. Open a
+terminal window and run the following command to install minitest:
+
+    gem install minitest
+
+If you would like color output, you can `require 'minitest/pride'` in
+the test file, or note the alternative instruction, below, for running
+the test file.
+
+Run the tests from the exercise directory using the following command:
+
+    ruby flatten_array_test.rb
+
+To include color from the command line:
+
+    ruby -r minitest/pride flatten_array_test.rb
+
+
+## Source
+
+Interview Question [https://reference.wolfram.com/language/ref/Flatten.html](https://reference.wolfram.com/language/ref/Flatten.html)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
diff --git a/ruby/flatten-array/flatten_array.rb b/ruby/flatten-array/flatten_array.rb
new file mode 100644
index 0000000..6af3960
--- /dev/null
+++ b/ruby/flatten-array/flatten_array.rb
@@ -0,0 +1,16 @@
+class FlattenArray
+  def self.flatten(array)
+    recursive_flatten(array)
+  end
+
+  def self.recursive_flatten(array, result = [])
+    array.each do |a|
+      if a.is_a? Array
+        recursive_flatten(a, result)
+      else
+        result << a unless a.nil?
+      end
+    end
+    result
+  end
+end
diff --git a/ruby/flatten-array/flatten_array_test.rb b/ruby/flatten-array/flatten_array_test.rb
new file mode 100644
index 0000000..47803a2
--- /dev/null
+++ b/ruby/flatten-array/flatten_array_test.rb
@@ -0,0 +1,41 @@
+require 'minitest/autorun'
+require_relative 'flatten_array'
+
+# Common test data version: 1.2.0 0290376
+class FlattenArrayTest < Minitest::Test
+  def test_no_nesting
+    # skip
+    flat_array = FlattenArray.flatten([0, 1, 2])
+    assert_equal [0, 1, 2], flat_array
+  end
+
+  def test_flattens_array_with_just_integers_present
+    # skip
+    flat_array = FlattenArray.flatten([1, [2, 3, 4, 5, 6, 7], 8])
+    assert_equal [1, 2, 3, 4, 5, 6, 7, 8], flat_array
+  end
+
+  def test_5_level_nesting
+    # skip
+    flat_array = FlattenArray.flatten([0, 2, [[2, 3], 8, 100, 4, [[[50]]]], -2])
+    assert_equal [0, 2, 2, 3, 8, 100, 4, 50, -2], flat_array
+  end
+
+  def test_6_level_nesting
+    # skip
+    flat_array = FlattenArray.flatten([1, [2, [[3]], [4, [[5]]], 6, 7], 8])
+    assert_equal [1, 2, 3, 4, 5, 6, 7, 8], flat_array
+  end
+
+  def test_6_level_nest_list_with_nil_values
+    # skip
+    flat_array = FlattenArray.flatten([0, 2, [[2, 3], 8, [[100]], nil, [[nil]]], -2])
+    assert_equal [0, 2, 2, 3, 8, 100, -2], flat_array
+  end
+
+  def test_all_values_in_nested_list_are_nil
+    # skip
+    flat_array = FlattenArray.flatten([nil, [[[nil]]], nil, nil, [[nil, nil], nil], nil])
+    assert_equal [], flat_array
+  end
+end