Added compress challenge.

arrays_strings/compress/compress_challenge.ipynb

@@ -0,0 +1,173 @@
+{
+ "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: Compress a string such that 'AAABCCDDDD' becomes 'A3B1C2D4'\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",
+    "* Can we 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\n",
+    "* Do you compress even if it doesn't save space?\n",
+    "    * No"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "* None -> None\n",
+    "* '' -> ''\n",
+    "* 'AABBCC' -> 'AABBCC'\n",
+    "* 'AAABCCDDDD' -> 'A3B1C2D4'"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/coding-challenges/blob/master/arrays_strings/compress/compress_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 compress_string(string):\n",
+    "    # TODO: Implement me\n",
+    "    pass"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "\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_compress.py\n",
+    "from nose.tools import assert_equal\n",
+    "\n",
+    "\n",
+    "class TestCompress(object):\n",
+    "    \n",
+    "    def test_compress(self, func):\n",
+    "        assert_equal(func(None), None)\n",
+    "        assert_equal(func(''), '')\n",
+    "        assert_equal(func('AABBCC'), 'AABBCC')\n",
+    "        assert_equal(func('AAABCCDDDD'), 'A3B1C2D4')\n",
+    "        print('Success: test_compress')\n",
+    "\n",
+    "def main():\n",
+    "    test = TestCompress()\n",
+    "    test.test_compress(compress_string)\n",
+    "    try:\n",
+    "        test.test_compress(compress_string_alt)\n",
+    "    except NameError:\n",
+    "        # Alternate solutions are only defined\n",
+    "        # in the solutions file\n",
+    "        pass\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/arrays_strings/compress/compress_solution.ipynb) for a discussion on algorithms and code solutions."
+   ]
+  }
+ ],
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+   "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",
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