Reworked notebook: Added more detail to constraints and test cases. Reworked code and unit test.

linked-lists/delete-mid.ipynb

@@ -13,20 +13,25 @@
    "source": [
     "## Problem: Delete a node in the middle, given only access to that node.\n",
     "\n",
-    "* [Clarifying Questions](#Clarifying-Questions)\n",
+    "* [Constraints and Assumptions](#Constraints-and-Assumptions)\n",
     "* [Test Cases](#Test-Cases)\n",
     "* [Algorithm](#Algorithm)\n",
-    "* [Code](#Code)"
+    "* [Code](#Code)\n",
+    "* [Unit Test](#Unit-Test)"
    ]
   },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Clarifying Questions\n",
+    "## Constraints and Assumptions\n",
     "\n",
-    "* What if the final node is being deleted, for example a single node list?\n",
-    "    * Make it a dummy node"
+    "*Problem statements are often intentionally ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
+    "\n",
+    "* What if the final node is being deleted, for example a single node list?  Do we make it a dummy with a NULL value?\n",
+    "    * Yes\n",
+    "* Can we assume we already have a linked list class that can be used for this problem?\n",
+    "    * Yes"
    ]
   },
   {
@@ -67,7 +72,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "metadata": {
     "collapsed": true
    },
@@ -78,9 +83,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {
-    "collapsed": true
+    "collapsed": false
    },
    "outputs": [],
    "source": [
@@ -95,39 +100,77 @@
     "            return\n",
     "        if node is None:\n",
     "            return\n",
-    "        next = node.next\n",
-    "        if next is None:\n",
+    "        node_next = node.next\n",
+    "        if node_next is None:\n",
     "            node.data = None\n",
     "            node.next = None\n",
     "        else:\n",
-    "            node.data = next.data\n",
-    "            node.next = next.next"
+    "            node.data = node_next.data\n",
+    "            node.next = node_next.next"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "*It is important to identify and run through general and edge cases from the [Test Cases](#Test-Cases) section by hand.  You generally will not be asked to write a unit test like what is shown below.*"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 3,
    "metadata": {
     "collapsed": false
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Test: Empty list, null node to delete\n",
+      "Test: One node\n",
+      "Test: Multiple nodes\n",
+      "Success: test_delete_node\n"
+     ]
+    }
+   ],
    "source": [
-    "# Empty list\n",
-    "linked_list = LinkedList(None)\n",
-    "linked_list.delete_node(None)\n",
-    "linked_list.print_list()\n",
-    "# One node\n",
-    "head = Node(2)\n",
-    "linked_list = LinkedList(head)\n",
-    "linked_list.delete_node(head)\n",
-    "linked_list.print_list()\n",
-    "# Multiple nodes\n",
-    "node0 = linked_list.insert_to_front(1)\n",
-    "node1 = linked_list.insert_to_front(3)\n",
-    "node2 = linked_list.insert_to_front(4)\n",
-    "node3 = linked_list.insert_to_front(1)\n",
-    "linked_list.delete_node(node2)\n",
-    "linked_list.print_list()"
+    "from nose.tools import assert_equal\n",
+    "\n",
+    "class Test(object):\n",
+    "    def test_delete_node(self):\n",
+    "        print('Test: Empty list, null node to delete')\n",
+    "        linked_list = MyLinkedList(None)\n",
+    "        linked_list.delete_node(None)\n",
+    "        assert_equal(linked_list.get_all_data(), [])\n",
+    "\n",
+    "        print('Test: One node')\n",
+    "        head = Node(2)\n",
+    "        linked_list = MyLinkedList(head)\n",
+    "        linked_list.delete_node(head)\n",
+    "        assert_equal(linked_list.get_all_data(), [None])\n",
+    "\n",
+    "        print('Test: Multiple nodes')\n",
+    "        linked_list = MyLinkedList(None)        \n",
+    "        node0 = linked_list.insert_to_front(1)\n",
+    "        node1 = linked_list.insert_to_front(3)\n",
+    "        node2 = linked_list.insert_to_front(4)\n",
+    "        node3 = linked_list.insert_to_front(1)\n",
+    "        linked_list.delete_node(node2)\n",
+    "        assert_equal(linked_list.get_all_data(), [1, 3, 1])\n",
+    "        \n",
+    "        print('Success: test_delete_node')\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    test = Test()\n",
+    "    test.test_delete_node()"
    ]
   }
  ],