Added stack challenge.

stacks_queues/stack/stack_solution.ipynb

@@ -4,7 +4,14 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://bit.ly/code-notes).</i></small>"
+    "<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/coding-challenges).</i></small>"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Solution Notebook"
    ]
   },
   {
@@ -27,7 +34,7 @@
    "source": [
     "## Constraints\n",
     "\n",
-    "*Problem statements are often intentionally ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
+    "*Problem statements are sometimes ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
     "\n",
     "* None"
    ]
@@ -130,13 +137,14 @@
    ],
    "source": [
     "%%writefile stack.py\n",
-    "\n",
     "class Node(object):\n",
+    "    \n",
     "    def __init__(self, data):\n",
     "        self.data = data\n",
     "        self.next = None\n",
     "\n",
     "class Stack(object):\n",
+    "    \n",
     "    def __init__(self, top=None):\n",
     "        self.top = top\n",
     "\n",
@@ -177,8 +185,7 @@
    "metadata": {},
    "source": [
     "## Unit Test\n",
-    "\n",
-    "*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.*"
+    "\n"
    ]
   },
   {
@@ -192,17 +199,17 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "Test: Empty stack\n",
-      "Test: One element\n",
-      "Test: More than one element\n",
-      "Success: test_end_to_end\n"
+      "Overwriting test_stack.py\n"
      ]
     }
    ],
    "source": [
+    "%%writefile test_stack.py\n",
     "from nose.tools import assert_equal\n",
     "\n",
-    "class Test(object):\n",
+    "\n",
+    "class TestStack(object):\n",
+    "    \n",
     "    # TODO: It would be better if we had unit tests for each\n",
     "    # method in addition to the following end-to-end test\n",
     "    def test_end_to_end(self):\n",
@@ -233,9 +240,34 @@
     "        \n",
     "        print('Success: test_end_to_end')\n",
     "\n",
+    "def main():\n",
+    "    test = TestStack()\n",
+    "    test.test_end_to_end()\n",
+    "    \n",
     "if __name__ == '__main__':\n",
-    "    test = Test()\n",
-    "    test.test_end_to_end()"
+    "    main()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Test: Empty stack\n",
+      "Test: One element\n",
+      "Test: More than one element\n",
+      "Success: test_end_to_end\n"
+     ]
+    }
+   ],
+   "source": [
+    "%run -i test_stack.py"
    ]
   },
   {