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

stacks-queues/stack-min.ipynb

@@ -13,19 +13,24 @@
    "source": [
     "## Problem: Implement a stack with push, pop, and min methods running O(1) time.\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",
-    "* Is this a stack of ints?\n",
+    "*Problem statements are often intentionally ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
+    "\n",
+    "* Can we assume this is a stack of ints?\n",
+    "    * Yes\n",
+    "* Can we assume we already have a stack class that can be used for this problem?\n",
     "    * Yes"
    ]
   },
@@ -49,7 +54,7 @@
     "\n",
     "### Min\n",
     "\n",
-    "* If the second stack is empty, return the max int value\n",
+    "* If the second stack is empty, return an error code (max int value)\n",
     "* Else, return the top of the stack, without popping it\n",
     "\n",
     "Complexity:\n",
@@ -87,7 +92,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "metadata": {
     "collapsed": true
    },
@@ -98,7 +103,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {
     "collapsed": true
    },
@@ -129,31 +134,71 @@
     "        return data"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "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.*"
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 3,
    "metadata": {
     "collapsed": false
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Test: Push on empty stack, non-empty stack\n",
+      "Test: Pop on non-empty stack\n",
+      "Test: Pop empty stack\n",
+      "Success: test_stack_min\n"
+     ]
+    }
+   ],
    "source": [
-    "print('Push on empty stack, non-empty stack')\n",
-    "stack = MyStack()\n",
-    "stack.push(5)\n",
-    "print('Push:', stack.peek(), 'Min after push:', stack.min())\n",
-    "stack.push(1)\n",
-    "print('Push:', stack.peek(), 'Min after push:', stack.min())\n",
-    "stack.push(3)\n",
-    "print('Push:', stack.peek(), 'Min after push:', stack.min())\n",
-    "stack.push(0)\n",
-    "print('Push:', stack.peek(), 'Min after push:', stack.min())\n",
-    "print('Pop on non-empty stack')\n",
-    "print('Pop:', stack.pop(), 'Min after pop:', stack.min())\n",
-    "print('Pop:', stack.pop(), 'Min after pop:', stack.min())\n",
-    "print('Pop:', stack.pop(), 'Min after pop:', stack.min())\n",
-    "print('Pop:', stack.pop(), 'Min after pop:', stack.min())\n",
-    "print('Stack contents:', stack.peek())\n",
-    "print('Pop empty stack:', stack.pop())"
+    "from nose.tools import assert_equal\n",
+    "\n",
+    "class Test(object):\n",
+    "    def test_stack_min(self):\n",
+    "        print('Test: Push on empty stack, non-empty stack')\n",
+    "        stack = MyStack()\n",
+    "        stack.push(5)\n",
+    "        assert_equal(stack.peek(), 5)\n",
+    "        assert_equal(stack.min(), 5)\n",
+    "        stack.push(1)\n",
+    "        assert_equal(stack.peek(), 1)\n",
+    "        assert_equal(stack.min(), 1)\n",
+    "        stack.push(3)\n",
+    "        assert_equal(stack.peek(), 3)\n",
+    "        assert_equal(stack.min(), 1)\n",
+    "        stack.push(0)\n",
+    "        assert_equal(stack.peek(), 0)\n",
+    "        assert_equal(stack.min(), 0)\n",
+    "\n",
+    "        print('Test: Pop on non-empty stack')\n",
+    "        assert_equal(stack.pop(), 0)\n",
+    "        assert_equal(stack.min(), 1)\n",
+    "        assert_equal(stack.pop(), 3)\n",
+    "        assert_equal(stack.min(), 1)\n",
+    "        assert_equal(stack.pop(), 1)\n",
+    "        assert_equal(stack.min(), 5)\n",
+    "        assert_equal(stack.pop(), 5)\n",
+    "        assert_equal(stack.min(), sys.maxint)\n",
+    "\n",
+    "        print('Test: Pop empty stack')\n",
+    "        assert_equal(stack.pop(), None)\n",
+    "        \n",
+    "        print('Success: test_stack_min')\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    test = Test()\n",
+    "    test.test_stack_min()"
    ]
   }
  ],