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Add bits to flip challenge
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‎bit_manipulation/bits_to_flip/__init__.py

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‎bit_manipulation/bits_to_flip/bits_to_flip_challenge.ipynb

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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: Determine the number of bits to flip to convert int a to int b'.\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 A and B are always ints?\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 A and B are always the same number of bits?\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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"* A or B is None -> Exception\n",
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"* General case\n",
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"<pre>\n",
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" A = 11101\n",
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" B = 01111\n",
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" Result: 2\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 bits_to_flip(self, a, b):\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_bits_to_flip.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_bits_to_flip(self):\n",
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" bits = Bits()\n",
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" a = int('11101', base=2)\n",
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" b = int('01111', base=2)\n",
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" expected = 2\n",
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" assert_equal(bits.bits_to_flip(a, b), expected)\n",
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" print('Success: test_bits_to_flip')\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_bits_to_flip()\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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}

‎bit_manipulation/bits_to_flip/bits_to_flip_solution.ipynb

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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: Determine the number of bits to flip to convert int a to int b.\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 A and B are always ints?\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 A and B are always the same number of bits?\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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"* A or B is None -> Exception\n",
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"* General case\n",
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"<pre>\n",
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" A = 11101\n",
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" B = 01111\n",
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" Result: 2\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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"We can use the xor operator to determine the bit differences between a and b\n",
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"\n",
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"* Set count to 0\n",
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"* Set c to a xor b\n",
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"* Loop while c != 0:\n",
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" * Increment count if the LSB in c is a 1\n",
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" * We can check this by using a mask of 1\n",
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" * Right shift c by 1\n",
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"* Return the count\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 bits_to_flip(self, a, b):\n",
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" if a is None or b is None:\n",
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" raise TypeError('a or b cannot be None')\n",
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" count = 0\n",
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" c = a ^ b\n",
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" while c:\n",
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" count += c & 1\n",
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" c >>= 1\n",
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" return count"
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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_bits_to_flip.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_bits_to_flip.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_bits_to_flip(self):\n",
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" bits = Bits()\n",
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" a = int('11101', base=2)\n",
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" b = int('01111', base=2)\n",
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" expected = 2\n",
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" assert_equal(bits.bits_to_flip(a, b), expected)\n",
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" print('Success: test_bits_to_flip')\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_bits_to_flip()\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_bits_to_flip\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_bits_to_flip.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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}

‎bit_manipulation/bits_to_flip/test_bits_to_flip.py

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from nose.tools import assert_equal
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class TestBits(object):
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def test_bits_to_flip(self):
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bits = Bits()
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a = int('11101', base=2)
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b = int('01111', base=2)
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expected = 2
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assert_equal(bits.bits_to_flip(a, b), expected)
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print('Success: test_bits_to_flip')
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def main():
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test = TestBits()
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test.test_bits_to_flip()
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if __name__ == '__main__':
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main()

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