mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
synced 2024-03-22 13:11:13 +08:00
Add pairwise swap challenge
This commit is contained in:
Donne Martin
parent
dc4c01c690
commit
470b38cdc4
0
bit_manipulation/pairwise_swap/__init__.py
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0
bit_manipulation/pairwise_swap/__init__.py
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174
bit_manipulation/pairwise_swap/pairwise_swap_challenge.ipynb
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174
bit_manipulation/pairwise_swap/pairwise_swap_challenge.ipynb
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@ -0,0 +1,174 @@
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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"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)."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Challenge Notebook"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Problem: Swap the odd and even bits of a positive integer with as few operations as possible.\n",
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"\n",
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"* [Constraints](#Constraints)\n",
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"* [Test Cases](#Test-Cases)\n",
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"* [Algorithm](#Algorithm)\n",
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"* [Code](#Code)\n",
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"* [Unit Test](#Unit-Test)\n",
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"* [Solution Notebook](#Solution-Notebook)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Constraints\n",
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"\n",
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"* Can we assume the input is always a positive int?\n",
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" * Yes\n",
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"* Can we assume we're working with 32 bits?\n",
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" * Yes\n",
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"* Is the output an int?\n",
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" * Yes\n",
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"* Can we assume the inputs are valid (not None)?\n",
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" * No\n",
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"* Can we assume this fits memory?\n",
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" * Yes"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Test Cases\n",
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"\n",
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"* None -> Exception\n",
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"* 0 -> 0\n",
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"* -1 -> -1\n",
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"* General case\n",
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"<pre>\n",
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" input = 1001 1111 0110\n",
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" result = 0110 1111 1001\n",
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"<pre>"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Algorithm\n",
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"\n",
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"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."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Code"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"class Bits(object):\n",
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"\n",
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" def pairwise_swap(self, num):\n",
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" # TODO: Implement me\n",
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" pass"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Unit Test"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"**The following unit test is expected to fail until you solve the challenge.**"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"# %load test_pairwise_swap.py\n",
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"from nose.tools import assert_equal\n",
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"\n",
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"\n",
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"class TestBits(object):\n",
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"\n",
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" def test_pairwise_swap(self):\n",
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" bits = Bits()\n",
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" assert_equal(bits.pairwise_swap(0), 0)\n",
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" assert_equal(bits.pairwise_swap(1), 1)\n",
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" num = int('0000100111110110', base=2)\n",
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" expected = int('0000011011111001', base=2)\n",
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" assert_equal(bits.pairwise_swap(num), expected)\n",
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" print('Success: test_pairwise_swap')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestBits()\n",
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" test.test_pairwise_swap()\n",
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"\n",
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"\n",
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"if __name__ == '__main__':\n",
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" main()"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Solution Notebook\n",
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"\n",
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"Review the [Solution Notebook]() for a discussion on algorithms and code solutions."
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.5.0"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 0
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}
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219
bit_manipulation/pairwise_swap/pairwise_swap_solution.ipynb
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bit_manipulation/pairwise_swap/pairwise_swap_solution.ipynb
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@ -0,0 +1,219 @@
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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"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)."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Solution Notebook"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Problem: Swap the odd and even bits of a positive integer with as few operations as possible.\n",
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"\n",
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"* [Constraints](#Constraints)\n",
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"* [Test Cases](#Test-Cases)\n",
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"* [Algorithm](#Algorithm)\n",
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"* [Code](#Code)\n",
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"* [Unit Test](#Unit-Test)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Constraints\n",
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"\n",
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"* Can we assume the input is always a positive int?\n",
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" * Yes\n",
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"* Can we assume we're working with 32 bits?\n",
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" * Yes\n",
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"* Is the output an int?\n",
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" * Yes\n",
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"* Can we assume the inputs are valid (not None)?\n",
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" * No\n",
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"* Can we assume this fits memory?\n",
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" * Yes"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Test Cases\n",
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"\n",
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"* None -> Exception\n",
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"* 0 -> 0\n",
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"* -1 -> -1\n",
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"* General case\n",
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"<pre>\n",
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" input = 0000 1001 1111 0110\n",
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" result = 0000 0110 1111 1001\n",
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"<pre>"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Algorithm\n",
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"\n",
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"<pre>\n",
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"* Isolate the odd bits with a mask:\n",
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" 0000 1001 1111 0110 num\n",
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" 1010 1010 1010 1010 mask\n",
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" --------------------------------\n",
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" 0000 1000 1010 0010 num & mask\n",
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"\n",
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"* Shift the odd bits right:\n",
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" 0000 0100 0101 0001 odd\n",
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"\n",
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"* Isolate the even bits with a mask:\n",
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" 0000 1001 1111 0110 num\n",
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" 0101 0101 0101 0101 mask\n",
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" --------------------------------\n",
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" 0000 0001 0101 0100 num & mask\n",
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"\n",
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"* Shift the even bits left:\n",
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" 0000 0010 1010 1000 even\n",
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"\n",
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"* Return even | odd\n",
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" 0000 0100 0101 0001 odd\n",
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" 0000 0010 1010 1000 even\n",
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" --------------------------------\n",
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" 0000 0110 1111 1001 odd | even\n",
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"</pre>\n",
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"\n",
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"Complexity:\n",
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"* Time: O(b), where b is the number of bits\n",
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"* Space: O(b), where b is the number of bits"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Code"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"class Bits(object):\n",
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"\n",
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" def pairwise_swap(self, num):\n",
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" if num is None:\n",
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" raise TypeError('num cannot be None')\n",
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" if num == 0 or num == 1:\n",
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" return num\n",
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" odd = (num & int('1010101010101010', base=2)) >> 1\n",
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" even = (num & int('0101010101010101', base=2)) << 1\n",
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" return odd | even"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Unit Test"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 2,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Overwriting test_pairwise_swap.py\n"
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]
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}
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],
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"source": [
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"%%writefile test_pairwise_swap.py\n",
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"from nose.tools import assert_equal, assert_raises\n",
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"\n",
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"\n",
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"class TestBits(object):\n",
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"\n",
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" def test_pairwise_swap(self):\n",
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" bits = Bits()\n",
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" assert_equal(bits.pairwise_swap(0), 0)\n",
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" assert_equal(bits.pairwise_swap(1), 1)\n",
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" num = int('0000100111110110', base=2)\n",
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" expected = int('0000011011111001', base=2)\n",
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" assert_equal(bits.pairwise_swap(num), expected)\n",
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" assert_raises(TypeError, bits.pairwise_swap, None)\n",
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" \n",
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" print('Success: test_pairwise_swap')\n",
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"\n",
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"\n",
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"def main():\n",
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" test = TestBits()\n",
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" test.test_pairwise_swap()\n",
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"\n",
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"\n",
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"if __name__ == '__main__':\n",
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" main()"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 3,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Success: test_pairwise_swap\n"
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]
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}
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],
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"source": [
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"%run -i test_pairwise_swap.py"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.5.0"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 0
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}
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24
bit_manipulation/pairwise_swap/test_pairwise_swap.py
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24
bit_manipulation/pairwise_swap/test_pairwise_swap.py
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@ -0,0 +1,24 @@
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from nose.tools import assert_equal, assert_raises
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class TestBits(object):
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def test_pairwise_swap(self):
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bits = Bits()
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assert_equal(bits.pairwise_swap(0), 0)
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assert_equal(bits.pairwise_swap(1), 1)
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num = int('0000100111110110', base=2)
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expected = int('0000011011111001', base=2)
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assert_equal(bits.pairwise_swap(num), expected)
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assert_raises(TypeError, bits.pairwise_swap, None)
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print('Success: test_pairwise_swap')
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def main():
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test = TestBits()
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test.test_pairwise_swap()
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if __name__ == '__main__':
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main()
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