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Polish quicksort challenge and solution

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Add None input test case.  Remove difficult to read 'Pythonic' solution.  Update space complexity discussion.
This commit is contained in:
Donne Martin
2016-02-25 05:49:31 -05:00
parent 4b5ce09e6c
commit 15ed55a7d4
3 changed files with 34 additions and 61 deletions
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22
sorting_searching/quick_sort/quick_sort_challenge.ipynb
View File

@@ -44,6 +44,7 @@
"source": [ "source": [
"## Test Cases\n", "## Test Cases\n",
"\n", "\n",
"* None -> None\n",
"* Empty input -> []\n", "* Empty input -> []\n",
"* One element -> [element]\n", "* One element -> [element]\n",
"* Two or more elements" "* Two or more elements"
@@ -103,6 +104,11 @@
"\n", "\n",
"class TestQuickSort(object):\n", "class TestQuickSort(object):\n",
" def test_quick_sort(self, func):\n", " def test_quick_sort(self, func):\n",
" print('None input')\n",
" data = None\n",
" sorted_data = func(data)\n",
" assert_equal(sorted_data, None)\n",
"\n",
" print('Empty input')\n", " print('Empty input')\n",
" data = []\n", " data = []\n",
" sorted_data = func(data)\n", " sorted_data = func(data)\n",
@@ -124,12 +130,6 @@
"def main():\n", "def main():\n",
" test = TestQuickSort()\n", " test = TestQuickSort()\n",
" test.test_quick_sort(quick_sort)\n", " test.test_quick_sort(quick_sort)\n",
" try:\n",
" test.test_quick_sort(quick_sort_alt)\n",
" except NameError:\n",
" # Alternate solutions are only defined\n",
" # in the solutions file\n",
" pass\n",
"\n", "\n",
"\n", "\n",
"if __name__ == '__main__':\n", "if __name__ == '__main__':\n",
@@ -148,21 +148,21 @@
], ],
"metadata": { "metadata": {
"kernelspec": { "kernelspec": {
"display_name": "Python 2", "display_name": "Python 3",
"language": "python", "language": "python",
"name": "python2" "name": "python3"
}, },
"language_info": { "language_info": {
"codemirror_mode": { "codemirror_mode": {
"name": "ipython", "name": "ipython",
"version": 2 "version": 3
}, },
"file_extension": ".py", "file_extension": ".py",
"mimetype": "text/x-python", "mimetype": "text/x-python",
"name": "python", "name": "python",
"nbconvert_exporter": "python", "nbconvert_exporter": "python",
"pygments_lexer": "ipython2", "pygments_lexer": "ipython3",
"version": "2.7.10" "version": "3.4.3"
} }
}, },
"nbformat": 4, "nbformat": 4,

62
sorting_searching/quick_sort/quick_sort_solution.ipynb
View File

@@ -44,6 +44,7 @@
"source": [ "source": [
"## Test Cases\n", "## Test Cases\n",
"\n", "\n",
"* None -> None\n",
"* Empty input -> []\n", "* Empty input -> []\n",
"* One element -> [element]\n", "* One element -> [element]\n",
"* Two or more elements" "* Two or more elements"
@@ -69,7 +70,9 @@
"\n", "\n",
"Complexity:\n", "Complexity:\n",
"* Time: O(n log(n)) average, best, O(n^2) worst\n", "* Time: O(n log(n)) average, best, O(n^2) worst\n",
"* Space: O(n), n extra space, n recursion depth, generally not stable" "* Space: O(n+m), n = number of elements, m = recursion depth\n",
"\n",
"Most implementations are not stable."
] ]
}, },
{ {
@@ -91,7 +94,7 @@
"\n", "\n",
"\n", "\n",
"def quick_sort(data):\n", "def quick_sort(data):\n",
" if len(data) < 2:\n", " if data is None or len(data) < 2:\n",
" return data\n", " return data\n",
" left = []\n", " left = []\n",
" right = []\n", " right = []\n",
@@ -113,30 +116,6 @@
" return left + [pivot_value] + right" " return left + [pivot_value] + right"
] ]
}, },
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Pythonic-Code\n",
"\n",
"The following code from [Stack Overflow](http://stackoverflow.com/questions/18262306/quick-sort-with-python) is very concise, although it might be a little difficult to read:"
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"def quick_sort_alt(arr):\n",
" if len(arr) <= 1:\n",
" return arr\n",
" else:\n",
" return quick_sort_alt([x for x in arr[1:] if x < arr[0]]) + [arr[0]] + quick_sort_alt([x for x in arr[1:] if x >= arr[0]])"
]
},
{ {
"cell_type": "markdown", "cell_type": "markdown",
"metadata": {}, "metadata": {},
@@ -147,7 +126,7 @@
}, },
{ {
"cell_type": "code", "cell_type": "code",
"execution_count": 3, "execution_count": 2,
"metadata": { "metadata": {
"collapsed": false "collapsed": false
}, },
@@ -167,6 +146,11 @@
"\n", "\n",
"class TestQuickSort(object):\n", "class TestQuickSort(object):\n",
" def test_quick_sort(self, func):\n", " def test_quick_sort(self, func):\n",
" print('None input')\n",
" data = None\n",
" sorted_data = func(data)\n",
" assert_equal(sorted_data, None)\n",
"\n",
" print('Empty input')\n", " print('Empty input')\n",
" data = []\n", " data = []\n",
" sorted_data = func(data)\n", " sorted_data = func(data)\n",
@@ -188,12 +172,6 @@
"def main():\n", "def main():\n",
" test = TestQuickSort()\n", " test = TestQuickSort()\n",
" test.test_quick_sort(quick_sort)\n", " test.test_quick_sort(quick_sort)\n",
" try:\n",
" test.test_quick_sort(quick_sort_alt)\n",
" except NameError:\n",
" # Alternate solutions are only defined\n",
" # in the solutions file\n",
" pass\n",
"\n", "\n",
"\n", "\n",
"if __name__ == '__main__':\n", "if __name__ == '__main__':\n",
@@ -202,7 +180,7 @@
}, },
{ {
"cell_type": "code", "cell_type": "code",
"execution_count": 4, "execution_count": 3,
"metadata": { "metadata": {
"collapsed": false "collapsed": false
}, },
@@ -211,11 +189,7 @@
"name": "stdout", "name": "stdout",
"output_type": "stream", "output_type": "stream",
"text": [ "text": [
"Empty input\n", "None input\n",
"One element\n",
"Two or more elements\n",
"Success: test_quick_sort\n",
"\n",
"Empty input\n", "Empty input\n",
"One element\n", "One element\n",
"Two or more elements\n", "Two or more elements\n",
@@ -231,21 +205,21 @@
], ],
"metadata": { "metadata": {
"kernelspec": { "kernelspec": {
"display_name": "Python 2", "display_name": "Python 3",
"language": "python", "language": "python",
"name": "python2" "name": "python3"
}, },
"language_info": { "language_info": {
"codemirror_mode": { "codemirror_mode": {
"name": "ipython", "name": "ipython",
"version": 2 "version": 3
}, },
"file_extension": ".py", "file_extension": ".py",
"mimetype": "text/x-python", "mimetype": "text/x-python",
"name": "python", "name": "python",
"nbconvert_exporter": "python", "nbconvert_exporter": "python",
"pygments_lexer": "ipython2", "pygments_lexer": "ipython3",
"version": "2.7.10" "version": "3.4.3"
} }
}, },
"nbformat": 4, "nbformat": 4,

11
sorting_searching/quick_sort/test_quick_sort.py
View File

@@ -3,6 +3,11 @@ from nose.tools import assert_equal
class TestQuickSort(object): class TestQuickSort(object):
def test_quick_sort(self, func): def test_quick_sort(self, func):
print('None input')
data = None
sorted_data = func(data)
assert_equal(sorted_data, None)
print('Empty input') print('Empty input')
data = [] data = []
sorted_data = func(data) sorted_data = func(data)
@@ -24,12 +29,6 @@ class TestQuickSort(object):
def main(): def main():
test = TestQuickSort() test = TestQuickSort()
test.test_quick_sort(quick_sort) test.test_quick_sort(quick_sort)
try:
test.test_quick_sort(quick_sort_alt)
except NameError:
# Alternate solutions are only defined
# in the solutions file
pass
if __name__ == '__main__': if __name__ == '__main__':