Add pairwise swap challenge

bit_manipulation/pairwise_swap/pairwise_swap_challenge.ipynb

@@ -0,0 +1,174 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Challenge Notebook"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Problem: Swap the odd and even bits of a positive integer with as few operations as possible.\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",
+    "* Can we assume the input is always a positive int?\n",
+    "    * Yes\n",
+    "* Can we assume we're working with 32 bits?\n",
+    "    * Yes\n",
+    "* Is the output an int?\n",
+    "    * Yes\n",
+    "* Can we assume the inputs are valid (not None)?\n",
+    "    * No\n",
+    "* Can we assume this fits memory?\n",
+    "    * Yes"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "* None -> Exception\n",
+    "* 0 -> 0\n",
+    "* -1 -> -1\n",
+    "* General case\n",
+    "<pre>\n",
+    "    input  = 1001 1111 0110\n",
+    "    result = 0110 1111 1001\n",
+    "<pre>"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "Refer to the [Solution Notebook]().  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": [
+    "class Bits(object):\n",
+    "\n",
+    "    def pairwise_swap(self, num):\n",
+    "        # TODO: Implement me\n",
+    "        pass"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**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_pairwise_swap.py\n",
+    "from nose.tools import assert_equal\n",
+    "\n",
+    "\n",
+    "class TestBits(object):\n",
+    "\n",
+    "    def test_pairwise_swap(self):\n",
+    "        bits = Bits()\n",
+    "        assert_equal(bits.pairwise_swap(0), 0)\n",
+    "        assert_equal(bits.pairwise_swap(1), 1)\n",
+    "        num = int('0000100111110110', base=2)\n",
+    "        expected = int('0000011011111001', base=2)\n",
+    "        assert_equal(bits.pairwise_swap(num), expected)\n",
+    "        print('Success: test_pairwise_swap')\n",
+    "\n",
+    "\n",
+    "def main():\n",
+    "    test = TestBits()\n",
+    "    test.test_pairwise_swap()\n",
+    "\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    main()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Solution Notebook\n",
+    "\n",
+    "Review the [Solution Notebook]() for a discussion on algorithms and code solutions."
+   ]
+  }
+ ],
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