diff --git a/hackerrank_topcoder/maximizing_xor/__init__.py b/hackerrank_topcoder/maximizing_xor/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/hackerrank_topcoder/maximizing_xor/maximizing_xor.ipynb b/hackerrank_topcoder/maximizing_xor/maximizing_xor.ipynb
index 58e6e1f..7fd4b71 100644
--- a/hackerrank_topcoder/maximizing_xor/maximizing_xor.ipynb
+++ b/hackerrank_topcoder/maximizing_xor/maximizing_xor.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"
    ]
   },
   {
@@ -13,10 +20,33 @@
    "source": [
     "## Problem: Maximizing XOR\n",
     "\n",
-    "From HackerRank: https://www.hackerrank.com/challenges/maximizing-xor\n",
+    "See the [HackerRank problem page](https://www.hackerrank.com/challenges/maximizing-xor).\n",
     "\n",
+    "* [Constraints](#Constraints)\n",
+    "* [Test Cases](#Test-Cases)\n",
     "* [Algorithm](#Algorithm)\n",
-    "* [Code](#Code)"
+    "* [Code](#Code)\n",
+    "* [Unit Test](#Unit-Test)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Constraints\n",
+    "\n",
+    "*Problem statements are sometimes ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
+    "\n",
+    "See the [HackerRank problem page](https://www.hackerrank.com/challenges/maximizing-xor)."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "See the [HackerRank problem page](https://www.hackerrank.com/challenges/maximizing-xor)."
    ]
   },
   {
@@ -45,7 +75,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "metadata": {
     "collapsed": false
    },
@@ -58,13 +88,68 @@
     "            curr = l ^ u\n",
     "            if result < curr:\n",
     "                result = curr\n",
-    "    return result\n",
+    "    return result"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Overwriting test_maximizing_xor.py\n"
+     ]
+    }
+   ],
+   "source": [
+    "%%writefile test_maximizing_xor.py\n",
+    "from nose.tools import assert_equal\n",
     "\n",
-    "lower = int(raw_input());\n",
-    "upper = int(raw_input());\n",
     "\n",
-    "result = max_xor(lower, upper);\n",
-    "print(result)"
+    "class TestMaximingXor(object):\n",
+    "\n",
+    "    def test_maximizing_xor(self):\n",
+    "        assert_equal(max_xor(10, 15), 7)\n",
+    "        print('Success: test_maximizing_xor')\n",
+    "\n",
+    "def main():\n",
+    "    test = TestMaximingXor()\n",
+    "    test.test_maximizing_xor()\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    main()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Success: test_maximizing_xor\n"
+     ]
+    }
+   ],
+   "source": [
+    "%run -i test_maximizing_xor.py"
    ]
   }
  ],
diff --git a/hackerrank_topcoder/maximizing_xor/maximizing_xor_challenge.ipynb b/hackerrank_topcoder/maximizing_xor/maximizing_xor_challenge.ipynb
new file mode 100644
index 0000000..9fd56f4
--- /dev/null
+++ b/hackerrank_topcoder/maximizing_xor/maximizing_xor_challenge.ipynb
@@ -0,0 +1,148 @@
+{
+ "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://github.com/donnemartin/coding-challenges).</i></small>"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Challenge Notebook"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Problem: Maximizing XOR\n",
+    "\n",
+    "See the [HackerRank problem page](https://www.hackerrank.com/challenges/maximizing-xor).\n",
+    "\n",
+    "* [Constraints](#Constraints)\n",
+    "* [Test Cases](#Test-Cases)\n",
+    "* [Algorithm](#Algorithm)\n",
+    "* [Code](#Code)\n",
+    "* [Unit Test](#Unit-Test)\n",
+    "* [Solution Notebook](#Solution-Notebook)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Constraints\n",
+    "\n",
+    "*Problem statements are sometimes ambiguous.  Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\n",
+    "\n",
+    "See the [HackerRank problem page](https://www.hackerrank.com/challenges/maximizing-xor)."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "See the [HackerRank problem page](https://www.hackerrank.com/challenges/maximizing-xor)."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/coding-challenges/blob/master/hackerrank_topcoder/utopian_tree/maximizing_xor_solution.ipynb).  If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Code"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [],
+   "source": [
+    "def max_xor(lower, upper):\n",
+    "    # TODO: Implement me\n",
+    "    pass"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test\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_maximizing_xor.py\n",
+    "from nose.tools import assert_equal\n",
+    "\n",
+    "\n",
+    "class TestMaximingXor(object):\n",
+    "\n",
+    "    def test_maximizing_xor(self):\n",
+    "        assert_equal(max_xor(10, 15), 7)\n",
+    "        print('Success: test_maximizing_xor')\n",
+    "\n",
+    "def main():\n",
+    "    test = TestMaximingXor()\n",
+    "    test.test_maximizing_xor()\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    main()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Solution Notebook\n",
+    "\n",
+    "Review the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/coding-challenges/blob/master/hackerrank_topcoder/utopian_tree/maximizing_xor_solution.ipynb) for a discussion on algorithms and code solutions."
+   ]
+  }
+ ],
+ "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
+}
diff --git a/hackerrank_topcoder/maximizing_xor/test_maximizing_xor.py b/hackerrank_topcoder/maximizing_xor/test_maximizing_xor.py
new file mode 100644
index 0000000..5be8601
--- /dev/null
+++ b/hackerrank_topcoder/maximizing_xor/test_maximizing_xor.py
@@ -0,0 +1,15 @@
+from nose.tools import assert_equal
+
+
+class TestMaximingXor(object):
+
+    def test_maximizing_xor(self):
+        assert_equal(max_xor(10, 15), 7)
+        print('Success: test_maximizing_xor')
+
+def main():
+    test = TestMaximingXor()
+    test.test_maximizing_xor()
+
+if __name__ == '__main__':
+    main()
\ No newline at end of file