Splice ./universe directory into ./

Manually merging:
- README.md: I added the description from universe/README.md into the heading of
  dotfiles/README.md.
- .envrc: dotfiles/.envrc was a superset of universe/.envrc
- .gitignore: Adding some of the ignored patterns from universe/.gitignore to
  dotfiles/.gitignore

Everything else here should be a simple rename.

1 files changed, 60 insertions, 0 deletions

diff --git a/data_structures_and_algorithms/delete-node.py b/data_structures_and_algorithms/delete-node.py
new file mode 100644
index 000000000000..7e431e224962
--- /dev/null
+++ b/data_structures_and_algorithms/delete-node.py
@@ -0,0 +1,60 @@
+import unittest
+
+
+################################################################################
+# Solution
+################################################################################
+def delete_node(x):
+    if not x.next:
+        raise Exception('Cannot delete the last node in a linked list.')
+    else:
+        x.value = x.next.value
+        x.next = x.next.next
+
+
+################################################################################
+# Tests
+################################################################################
+class Test(unittest.TestCase):
+    class LinkedListNode(object):
+        def __init__(self, value, next=None):
+            self.value = value
+            self.next = next
+
+        def get_values(self):
+            node = self
+            values = []
+            while node is not None:
+                values.append(node.value)
+                node = node.next
+            return values
+
+    def setUp(self):
+        self.fourth = Test.LinkedListNode(4)
+        self.third = Test.LinkedListNode(3, self.fourth)
+        self.second = Test.LinkedListNode(2, self.third)
+        self.first = Test.LinkedListNode(1, self.second)
+
+    def test_node_at_beginning(self):
+        delete_node(self.first)
+        actual = self.first.get_values()
+        expected = [2, 3, 4]
+        self.assertEqual(actual, expected)
+
+    def test_node_in_middle(self):
+        delete_node(self.second)
+        actual = self.first.get_values()
+        expected = [1, 3, 4]
+        self.assertEqual(actual, expected)
+
+    def test_node_at_end(self):
+        with self.assertRaises(Exception):
+            delete_node(self.fourth)
+
+    def test_one_node_in_list(self):
+        unique = Test.LinkedListNode(1)
+        with self.assertRaises(Exception):
+            delete_node(unique)
+
+
+unittest.main(verbosity=2)