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Add radix sort challenge

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Donne Martin 2017-03-27 05:15:24 -04:00
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0
sorting_searching/radix_sort/__init__.py Normal file
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sorting_searching/radix_sort/radix_sort_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: Implement radix sort.\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",
"* Is the input a list?\n",
" * Yes\n",
"* Can we assume the inputs are valid?\n",
" * Check for None in place of an array\n",
" * Assume array elements are ints\n",
"* Do we know the max digits to handle?\n",
" * No\n",
"* Are the digits base 10?\n",
" * Yes\n",
"* Can we assume this fits memory?\n",
" * Yes"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Test Cases\n",
"\n",
"* None -> Exception\n",
"* [] -> []\n",
"* [128, 256, 164, 8, 2, 148, 212, 242, 244] -> [2, 8, 128, 148, 164, 212, 242, 244, 256]"
]
},
{
"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 RadixSort(object):\n",
"\n",
" def sort(self, array, base=10):\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_radix_sort.py\n",
"from nose.tools import assert_equal, assert_raises\n",
"\n",
"\n",
"class TestRadixSort(object):\n",
"\n",
" def test_sort(self):\n",
" radix_sort = RadixSort()\n",
" assert_raises(TypeError, radix_sort.sort, None)\n",
" assert_equal(radix_sort.sort([]), [])\n",
" array = [128, 256, 164, 8, 2, 148, 212, 242, 244]\n",
" expected = [2, 8, 128, 148, 164, 212, 242, 244, 256]\n",
" assert_equal(radix_sort.sort(array), expected)\n",
" print('Success: test_sort')\n",
"\n",
"\n",
"def main():\n",
" test = TestRadixSort()\n",
" test.test_sort()\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"
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},
"nbformat": 4,
"nbformat_minor": 0
}

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sorting_searching/radix_sort/radix_sort_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: Implement radix sort.\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",
"* Is the input a list?\n",
" * Yes\n",
"* Can we assume the inputs are valid?\n",
" * Check for None in place of an array\n",
" * Assume array elements are ints\n",
"* Do we know the max digits to handle?\n",
" * No\n",
"* Are the digits base 10?\n",
" * Yes\n",
"* Can we assume this fits memory?\n",
" * Yes"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Test Cases\n",
"\n",
"* None -> Exception\n",
"* [] -> []\n",
"* [128, 256, 164, 8, 2, 148, 212, 242, 244] -> [2, 8, 128, 148, 164, 212, 242, 244, 256]"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Algorithm\n",
"\n",
"Sample input: [1, 220, 122, 112]\n",
"\n",
"* We'll evaluate each digit starting with the ones position\n",
" * [**1**, 22**0**, 12**2**, 11**2**]\n",
" * Bucket 0: 220\n",
" * Bucket 1: 1\n",
" * Bucket 2: 122, 112\n",
" * Result: [220, 1, 122, 112]\n",
" * [2**2**0, 1, 1**2**2, 1**1**2]\n",
" * Bucket 0: 1\n",
" * Bucket 1: 112\n",
" * Bucket 2: 220, 122\n",
" * Result: [1, 112, 220, 122]\n",
" * [1, **1**12, **2**20, **1**22]\n",
" * Bucket 0: 1\n",
" * Bucket 1: 112, 122\n",
" * Bucket 2: 220\n",
" * Result: [1, 112, 122, 220]\n",
"\n",
"Bucketing example: 123\n",
"\n",
"* Ones\n",
" * 12**3** // 10^0 = 123\n",
" * 123 % 10 = 3\n",
"* Tens\n",
" * 1**2**3 // 10^1 = 12\n",
" * 12 % 10 = 2\n",
"* Hundreds\n",
" * **1**23 // 10^2 = 1\n",
" * 1 % 10 = 1\n",
"\n",
"Complexity:\n",
"* Time: O(k*n), where n is the number of items and k is the number of digits in the largest item\n",
"* Space: O(k+n)\n",
"\n",
"Misc:\n",
"* Not in-place\n",
"* Most implementations are stable\n",
"\n",
"If k (the number of digits) is less than log(n), radix sort can be faster than algorithms such as quicksort."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Code"
]
},
{
"cell_type": "code",
"execution_count": 1,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"class RadixSort(object):\n",
"\n",
" def sort(self, array, base=10):\n",
" if array is None:\n",
" raise TypeError('array cannot be None')\n",
" if not array:\n",
" return []\n",
" max_element = max(array)\n",
" max_digits = len(str(abs(max_element)))\n",
" curr_array = array\n",
" for digit in range(max_digits):\n",
" buckets = [[] for _ in range(base)]\n",
" for item in curr_array:\n",
" buckets[(item//(base**digit))%base].append(item)\n",
" curr_array = []\n",
" for bucket in buckets:\n",
" curr_array.extend(bucket)\n",
" return curr_array"
]
},
{
"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_radix_sort.py\n"
]
}
],
"source": [
"%%writefile test_radix_sort.py\n",
"from nose.tools import assert_equal, assert_raises\n",
"\n",
"\n",
"class TestRadixSort(object):\n",
"\n",
" def test_sort(self):\n",
" radix_sort = RadixSort()\n",
" assert_raises(TypeError, radix_sort.sort, None)\n",
" assert_equal(radix_sort.sort([]), [])\n",
" array = [128, 256, 164, 8, 2, 148, 212, 242, 244]\n",
" expected = [2, 8, 128, 148, 164, 212, 242, 244, 256]\n",
" assert_equal(radix_sort.sort(array), expected)\n",
" print('Success: test_sort')\n",
"\n",
"\n",
"def main():\n",
" test = TestRadixSort()\n",
" test.test_sort()\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_sort\n"
]
}
],
"source": [
"%run -i test_radix_sort.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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sorting_searching/radix_sort/test_radix_sort.py Normal file
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from nose.tools import assert_equal, assert_raises
class TestRadixSort(object):
def test_sort(self):
radix_sort = RadixSort()
assert_raises(TypeError, radix_sort.sort, None)
assert_equal(radix_sort.sort([]), [])
array = [128, 256, 164, 8, 2, 148, 212, 242, 244]
expected = [2, 8, 128, 148, 164, 212, 242, 244, 256]
assert_equal(radix_sort.sort(array), expected)
print('Success: test_sort')
def main():
test = TestRadixSort()
test.test_sort()
if __name__ == '__main__':
main()