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

linked-lists/palindrome.ipynb

@@ -13,21 +13,25 @@
    "source": [
     "## Problem: Determine if a linked list is a palindrome.\n",
     "\n",
-    "* [Clarifying Questions](#Clarifying-Questions)\n",
+    "* [Constraints and Assumptions](#Constraints-and-Assumptions)\n",
     "* [Test Cases](#Test-Cases)\n",
     "* [Algorithm](#Algorithm)\n",
     "* [Code](#Code)\n",
-    "* [Pythonic-Code](#Pythonic-Code)"
+    "* [Unit Test](#Unit-Test)"
    ]
   },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Clarifying Questions\n",
+    "## Constraints and Assumptions\n",
+    "\n",
+    "*Problem statements are often intentionally ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
     "\n",
     "* Is a single character or number a palindrome?\n",
-    "    * No"
+    "    * No\n",
+    "* Can we assume we already have a linked list class that can be used for this problem?\n",
+    "    * Yes"
    ]
   },
   {
@@ -36,6 +40,7 @@
    "source": [
     "## Test Cases\n",
     "\n",
+    "\n",
     "* Empty list\n",
     "* Single element list\n",
     "* Two element list, not a palindrome\n",
@@ -71,7 +76,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "metadata": {
     "collapsed": true
    },
@@ -82,7 +87,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {
     "collapsed": false
    },
@@ -95,10 +100,15 @@
     "        curr = self.head\n",
     "        reversed_list = MyLinkedList()\n",
     "        length = 0\n",
+    "        \n",
+    "        # Reverse the linked list\n",
     "        while curr is not None:\n",
     "            reversed_list.insert_to_front(curr.data)\n",
     "            length += 1\n",
     "            curr = curr.next\n",
+    "            \n",
+    "        # Compare the reversed list with the original list\n",
+    "        # Only need to compare the first half            \n",
     "        iterations_to_compare_half = length / 2\n",
     "        curr = self.head\n",
     "        curr_reversed = reversed_list.head\n",
@@ -110,42 +120,85 @@
     "        return True"
    ]
   },
+  {
+   "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\n",
+      "Test: Single element list\n",
+      "Test: Two element list, not a palindrome\n",
+      "Test: Three element list, not a palindrome\n",
+      "Test: General case: Palindrome with even length\n",
+      "Test: General case: Palindrome with odd length\n",
+      "Success: test_is_palindrome\n"
+     ]
+    }
+   ],
    "source": [
-    "print('Empty list')\n",
+    "from nose.tools import assert_equal\n",
+    "\n",
+    "class Test(object):\n",
+    "    def test_is_palindrome(self):\n",
+    "        print('Test: Empty list')\n",
     "        linked_list = MyLinkedList()\n",
-    "print(linked_list.is_palindrome())\n",
+    "        assert_equal(linked_list.is_palindrome(), False)\n",
-    "print('Single element list')\n",
+    "\n",
+    "        print('Test: Single element list')\n",
     "        head = Node(1)\n",
     "        linked_list = MyLinkedList(head)\n",
-    "print(linked_list.is_palindrome())\n",
+    "        assert_equal(linked_list.is_palindrome(), False)\n",
-    "print('Two element list, not a palindrome')\n",
+    "\n",
+    "        print('Test: Two element list, not a palindrome')\n",
     "        linked_list.append(2)\n",
-    "print(linked_list.is_palindrome())\n",
+    "        assert_equal(linked_list.is_palindrome(), False)\n",
-    "print('Three element list, not a palindrome')\n",
+    "\n",
+    "        print('Test: Three element list, not a palindrome')\n",
     "        linked_list.append(3)\n",
-    "print(linked_list.is_palindrome())\n",
+    "        assert_equal(linked_list.is_palindrome(), False)\n",
-    "print('General case: Palindrome with even length')\n",
+    "\n",
+    "        print('Test: General case: Palindrome with even length')\n",
     "        head = Node('a')\n",
     "        linked_list = MyLinkedList(head)\n",
     "        linked_list.append('b')\n",
     "        linked_list.append('b')\n",
     "        linked_list.append('a')\n",
-    "print(linked_list.is_palindrome())\n",
+    "        assert_equal(linked_list.is_palindrome(), True)\n",
-    "print('General case: Palindrome with odd length')\n",
+    "\n",
+    "        print('Test: General case: Palindrome with odd length')\n",
     "        head = Node(1)\n",
     "        linked_list = MyLinkedList(head)\n",
     "        linked_list.append(2)\n",
     "        linked_list.append(3)\n",
     "        linked_list.append(2)\n",
     "        linked_list.append(1)\n",
-    "print(linked_list.is_palindrome())"
+    "        assert_equal(linked_list.is_palindrome(), True)\n",
+    "        \n",
+    "        print('Success: test_is_palindrome')\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    test = Test()\n",
+    "    test.test_is_palindrome()"
    ]
   }
  ],