Added rotation challenge and solution.

arrays_strings/rotation/rotation_challenge.ipynb

@@ -0,0 +1,136 @@
+{
+ "cells": [
+  {
+   "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>"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Problem: Determine if a string s1 is a rotation of another string s2, by calling (only once) a function is_substring\n",
+    "\n",
+    "* [Constraints and Assumptions](#Constraints-and-Assumptions)\n",
+    "* [Test Cases](#Test-Cases)\n",
+    "* [Algorithm](#Algorithm)\n",
+    "* [Code](#Code)\n",
+    "* [Unit Test](#Unit-Test)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "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",
+    "\n",
+    "* Can I assume the string is ASCII?\n",
+    "    * Yes\n",
+    "    * Note: Unicode strings could require special handling depending on your language\n",
+    "* Can you use additional data structures?  \n",
+    "    * Yes\n",
+    "* Is this case sensitive?\n",
+    "    * Yes"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "* Any strings that differ in size -> False\n",
+    "* None, 'foo' -> False (any None results in False)\n",
+    "* ' ', 'foo' -> False\n",
+    "* ' ', ' ' -> True\n",
+    "* 'foobarbaz', 'barbazfoo' -> True"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "Refer to the solution notebook for the algorithm."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Code"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "def is_substring(s1, s2):\n",
+    "    # TODO: Implement me\n",
+    "    pass\n",
+    "\n",
+    "def is_rotation(s1, s2):\n",
+    "    # TODO: Implement me\n",
+    "    # Call is_substring only once\n",
+    "    pass"
+   ]
+  },
+  {
+   "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.*\n",
+    "\n",
+    "**The following unit test is expected to fail until you solve the challenge.**"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "%load test_rotation.py"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 2",
+   "language": "python",
+   "name": "python2"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 2
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython2",
+   "version": "2.7.10"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}

arrays_strings/rotation/rotation_solution.ipynb

@@ -11,7 +11,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Problem: Determine if a string s1 is a rotation of another string s2.  Also write a function is_substring which you can only call once to determine whether a rotation occurs\n",
+    "## Problem: Determine if a string s1 is a rotation of another string s2, by calling (only once) a function is_substring\n",
     "\n",
     "* [Constraints and Assumptions](#Constraints-and-Assumptions)\n",
     "* [Test Cases](#Test-Cases)\n",
@@ -43,8 +43,8 @@
    "source": [
     "## Test Cases\n",
     "\n",
-    "* Any strings that differ in size results in False\n",
+    "* Any strings that differ in size -> False\n",
-    "* NULL, 'foo' -> False (any NULL results in False)\n",
+    "* None, 'foo' -> False (any None results in False)\n",
     "* ' ', 'foo' -> False\n",
     "* ' ', ' ' -> True\n",
     "* 'foobarbaz', 'barbazfoo' -> True"
@@ -121,25 +121,50 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "Success: test_is_rotation\n"
+      "Overwriting test_rotation.py\n"
      ]
     }
    ],
    "source": [
+    "%%writefile test_rotation.py\n",
     "from nose.tools import assert_equal\n",
     "\n",
-    "class Test(object):\n",
+    "\n",
-    "    def test_is_rotation(self, func):\n",
+    "class TestRotation(object):\n",
-    "        assert_equal(func('o', 'oo'), False)\n",
+    "    \n",
-    "        assert_equal(func(None, 'foo'), False)\n",
+    "    def test_rotation(self):\n",
-    "        assert_equal(func('', 'foo'), False)\n",
+    "        assert_equal(is_rotation('o', 'oo'), False)\n",
-    "        assert_equal(func('', ''), True)\n",
+    "        assert_equal(is_rotation(None, 'foo'), False)\n",
-    "        assert_equal(func('foobarbaz', 'barbazfoo'), True)\n",
+    "        assert_equal(is_rotation('', 'foo'), False)\n",
-    "        print('Success: test_is_rotation')\n",
+    "        assert_equal(is_rotation('', ''), True)\n",
+    "        assert_equal(is_rotation('foobarbaz', 'barbazfoo'), True)\n",
+    "        print('Success: test_rotation')\n",
+    "\n",
+    "def main():\n",
+    "    test = TestRotation()\n",
+    "    test.test_rotation()\n",
     "\n",
     "if __name__ == '__main__':\n",
-    "    test = Test()\n",
+    "    main()"
-    "    test.test_is_rotation(is_rotation)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Success: test_rotation\n"
+     ]
+    }
+   ],
+   "source": [
+    "%run -i test_rotation.py"
    ]
   }
  ],

arrays_strings/rotation/test_rotation.py

@@ -0,0 +1,19 @@
+from nose.tools import assert_equal
+
+
+class TestRotation(object):
+    
+    def test_rotation(self):
+        assert_equal(is_rotation('o', 'oo'), False)
+        assert_equal(is_rotation(None, 'foo'), False)
+        assert_equal(is_rotation('', 'foo'), False)
+        assert_equal(is_rotation('', ''), True)
+        assert_equal(is_rotation('foobarbaz', 'barbazfoo'), True)
+        print('Success: test_rotation')
+
+def main():
+    test = TestRotation()
+    test.test_rotation()
+
+if __name__ == '__main__':
+    main()