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Add bits to flip challenge

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Donne Martin 2017-03-31 04:45:28 -04:00
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0
bit_manipulation/bits_to_flip/__init__.py Normal file
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bit_manipulation/bits_to_flip/bits_to_flip_challenge.ipynb Normal file
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{
"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: Determine the number of bits to flip to convert int a to int b'.\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 A and B are always ints?\n",
" * Yes\n",
"* Is the output an int?\n",
" * Yes\n",
"* Can we assume A and B are always the same number of bits?\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",
"* A or B is None -> Exception\n",
"* General case\n",
"<pre>\n",
" A = 11101\n",
" B = 01111\n",
" Result: 2\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 bits_to_flip(self, a, b):\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_bits_to_flip.py\n",
"from nose.tools import assert_equal\n",
"\n",
"\n",
"class TestBits(object):\n",
"\n",
" def test_bits_to_flip(self):\n",
" bits = Bits()\n",
" a = int('11101', base=2)\n",
" b = int('01111', base=2)\n",
" expected = 2\n",
" assert_equal(bits.bits_to_flip(a, b), expected)\n",
" print('Success: test_bits_to_flip')\n",
"\n",
"\n",
"def main():\n",
" test = TestBits()\n",
" test.test_bits_to_flip()\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."
]
}
],
"metadata": {
"kernelspec": {
"display_name": "Python 3",
"language": "python",
"name": "python3"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 3
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython3",
"version": "3.5.0"
}
},
"nbformat": 4,
"nbformat_minor": 0
}

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bit_manipulation/bits_to_flip/bits_to_flip_solution.ipynb Normal file
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{
"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": [
"# Solution Notebook"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Problem: Determine the number of bits to flip to convert int a to int b.\n",
"\n",
"* [Constraints](#Constraints)\n",
"* [Test Cases](#Test-Cases)\n",
"* [Algorithm](#Algorithm)\n",
"* [Code](#Code)\n",
"* [Unit Test](#Unit-Test)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Constraints\n",
"\n",
"* Can we assume A and B are always ints?\n",
" * Yes\n",
"* Is the output an int?\n",
" * Yes\n",
"* Can we assume A and B are always the same number of bits?\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",
"* A or B is None -> Exception\n",
"* General case\n",
"<pre>\n",
" A = 11101\n",
" B = 01111\n",
" Result: 2\n",
"<pre>"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Algorithm\n",
"\n",
"We can use the xor operator to determine the bit differences between a and b\n",
"\n",
"* Set count to 0\n",
"* Set c to a xor b\n",
"* Loop while c != 0:\n",
" * Increment count if the LSB in c is a 1\n",
" * We can check this by using a mask of 1\n",
" * Right shift c by 1\n",
"* Return the count\n",
" \n",
"Complexity:\n",
"* Time: O(b), where b is the number of bits\n",
"* Space: O(b), where b is the number of bits"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Code"
]
},
{
"cell_type": "code",
"execution_count": 1,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"class Bits(object):\n",
"\n",
" def bits_to_flip(self, a, b):\n",
" if a is None or b is None:\n",
" raise TypeError('a or b cannot be None')\n",
" count = 0\n",
" c = a ^ b\n",
" while c:\n",
" count += c & 1\n",
" c >>= 1\n",
" return count"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Unit Test"
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Overwriting test_bits_to_flip.py\n"
]
}
],
"source": [
"%%writefile test_bits_to_flip.py\n",
"from nose.tools import assert_equal\n",
"\n",
"\n",
"class TestBits(object):\n",
"\n",
" def test_bits_to_flip(self):\n",
" bits = Bits()\n",
" a = int('11101', base=2)\n",
" b = int('01111', base=2)\n",
" expected = 2\n",
" assert_equal(bits.bits_to_flip(a, b), expected)\n",
" print('Success: test_bits_to_flip')\n",
"\n",
"\n",
"def main():\n",
" test = TestBits()\n",
" test.test_bits_to_flip()\n",
"\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_bits_to_flip\n"
]
}
],
"source": [
"%run -i test_bits_to_flip.py"
]
}
],
"metadata": {
"kernelspec": {
"display_name": "Python 3",
"language": "python",
"name": "python3"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 3
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython3",
"version": "3.5.0"
}
},
"nbformat": 4,
"nbformat_minor": 0
}

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