Reworked notebook: Added more detail to clarifying questions and test cases. Reworked algorithm discussion and unit test.

arrays-strings/permutation.ipynb

@@ -18,7 +18,8 @@
     "* [Algorithm: Compare Sorted Strings](#Algorithm:-Compare-Sorted-Strings)\n",
     "* [Code: Compare Sorted Strings](#Code:-Compare-Sorted-Strings)\n",
     "* [Algorithm: Hashmap Lookup](#Algorithm:-Hash-Map-Lookup)\n",
-    "* [Code: Hashmap Lookup](#Code:-Hash-Map-Lookup)"
+    "* [Code: Hashmap Lookup](#Code:-Hash-Map-Lookup)\n",
+    "* [Unit Test](#Unit-Test)"
    ]
   },
   {
@@ -27,8 +28,11 @@
    "source": [
     "## Clarifying Questions\n",
     "\n",
-    "* Is the string ASCII (extended)?  Or Unicode?\n",
-    "    * ASCII extended, which is 256 characters\n",
+    "*Problem statements are sometimes intentionally ambiguous.  Asking clarifying questions, identifying constraints, and stating assumptions help to ensure you code the intended solution.*\n",
+    "\n",
+    "* Can I assume the string is ASCII?\n",
+    "    * Yes\n",
+    "    * Note: Unicode strings could require special handling depending on your language\n",
     "* Is whitespace important?\n",
     "    * Yes\n",
     "* Is this case sensitive?  'Nib', 'bin' is not a match?\n",
@@ -41,34 +45,14 @@
    "source": [
     "## Test Cases\n",
     "\n",
+    "*Identifying and running through general and edge cases are important.  You generally will not be asked to write a unit test like what is shown below.*\n",
+    "\n",
     "* One or more empty strings -> False\n",
     "* 'Nib', 'bin' -> False\n",
     "* 'act', 'cat' -> True\n",
     "* 'a ct', 'ca t' -> True"
    ]
   },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {
-    "collapsed": false
-   },
-   "outputs": [],
-   "source": [
-    "from nose.tools import assert_equal\n",
-    "\n",
-    "class Test(object):\n",
-    "    def test_permutation(self, func):\n",
-    "        assert_equal(func('', 'foo'), False)\n",
-    "        assert_equal(func('Nib', 'bin'), False)\n",
-    "        assert_equal(func('act', 'cat'), True)\n",
-    "        assert_equal(func('a ct', 'ca t'), True)\n",
-    "\n",
-    "def run_tests(func):\n",
-    "    test = Test()\n",
-    "    test.test_permutation(func)"
-   ]
-  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -97,16 +81,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "metadata": {
     "collapsed": false
    },
    "outputs": [],
    "source": [
     "def permutations(str1, str2):\n",
-    "    return sorted(str1) == sorted(str2)\n",
-    "\n",
-    "run_tests(permutations)"
+    "    return sorted(str1) == sorted(str2)"
    ]
   },
   {
@@ -128,7 +110,7 @@
     "    * Return False\n",
     "\n",
     "Notes:\n",
-    "* Since the characters are in ASCII, we could potentially use an array of size 128 (or 256 for extended ASCII)\n",
+    "* Since the characters are in ASCII, we could potentially use an array of size 128 (or 256 for extended ASCII), where each array index is equivalent to an ASCII value\n",
     "* Instead of using two hash maps, you could use one hash map and increment character values based on the first string and decrement based on the second string\n",
     "* You can short circuit if the lengths of each string are not equal, len() in Python is generally O(1)\n",
     "\n",
@@ -146,7 +128,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {
     "collapsed": false
    },
@@ -165,9 +147,47 @@
     "        return False\n",
     "    unique_counts1 = unique_counts(str1)\n",
     "    unique_counts2 = unique_counts(str2)\n",
-    "    return unique_counts1 == unique_counts2\n",
+    "    return unique_counts1 == unique_counts2"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Success: test_permutation\n",
+      "Success: test_permutation\n"
+     ]
+    }
+   ],
+   "source": [
+    "from nose.tools import assert_equal\n",
     "\n",
-    "run_tests(permutations_alt)"
+    "class Test(object):\n",
+    "    def test_permutation(self, func):\n",
+    "        assert_equal(func('', 'foo'), False)\n",
+    "        assert_equal(func('Nib', 'bin'), False)\n",
+    "        assert_equal(func('act', 'cat'), True)\n",
+    "        assert_equal(func('a ct', 'ca t'), True)\n",
+    "        print('Success: test_permutation')\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    test = Test()\n",
+    "    test.test_permutation(permutations)\n",
+    "    test.test_permutation(permutations_alt)"
    ]
   }
  ],