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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": [
"## Test Cases\n",
"\n",
"* None -> None\n",
"* Empty input -> []\n",
"* One element -> [element]\n",
"* Two or more elements"
@ -103,6 +104,11 @@
"\n",
"class TestQuickSort(object):\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",
" data = []\n",
" sorted_data = func(data)\n",
@ -124,12 +130,6 @@
"def main():\n",
" test = TestQuickSort()\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",
"if __name__ == '__main__':\n",
@ -148,21 +148,21 @@
],
"metadata": {
"kernelspec": {
"display_name": "Python 2",
"display_name": "Python 3",
"language": "python",
"name": "python2"
"name": "python3"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 2
"version": 3
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython2",
"version": "2.7.10"
"pygments_lexer": "ipython3",
"version": "3.4.3"
}
},
"nbformat": 4,

62
sorting_searching/quick_sort/quick_sort_solution.ipynb
View File

@ -44,6 +44,7 @@
"source": [
"## Test Cases\n",
"\n",
"* None -> None\n",
"* Empty input -> []\n",
"* One element -> [element]\n",
"* Two or more elements"
@ -69,7 +70,9 @@
"\n",
"Complexity:\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",
"def quick_sort(data):\n",
" if len(data) < 2:\n",
" if data is None or len(data) < 2:\n",
" return data\n",
" left = []\n",
" right = []\n",
@ -113,30 +116,6 @@
" 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",
"metadata": {},
@ -147,7 +126,7 @@
},
{
"cell_type": "code",
"execution_count": 3,
"execution_count": 2,
"metadata": {
"collapsed": false
},
@ -167,6 +146,11 @@
"\n",
"class TestQuickSort(object):\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",
" data = []\n",
" sorted_data = func(data)\n",
@ -188,12 +172,6 @@
"def main():\n",
" test = TestQuickSort()\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",
"if __name__ == '__main__':\n",
@ -202,7 +180,7 @@
},
{
"cell_type": "code",
"execution_count": 4,
"execution_count": 3,
"metadata": {
"collapsed": false
},
@ -211,11 +189,7 @@
"name": "stdout",
"output_type": "stream",
"text": [
"Empty input\n",
"One element\n",
"Two or more elements\n",
"Success: test_quick_sort\n",
"\n",
"None input\n",
"Empty input\n",
"One element\n",
"Two or more elements\n",
@ -231,21 +205,21 @@
],
"metadata": {
"kernelspec": {
"display_name": "Python 2",
"display_name": "Python 3",
"language": "python",
"name": "python2"
"name": "python3"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 2
"version": 3
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython2",
"version": "2.7.10"
"pygments_lexer": "ipython3",
"version": "3.4.3"
}
},
"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):
def test_quick_sort(self, func):
print('None input')
data = None
sorted_data = func(data)
assert_equal(sorted_data, None)
print('Empty input')
data = []
sorted_data = func(data)
@ -24,12 +29,6 @@ class TestQuickSort(object):
def main():
test = TestQuickSort()
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__':