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Update quicksort challenge (#134)

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Update constraints, test cases, code, algorithm, and tests.
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Donne Martin 2016-12-29 07:21:56 -05:00 committed by GitHub
parent a6881bab68
commit 3d49bb1d43
3 changed files with 82 additions and 70 deletions
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40
sorting_searching/quick_sort/quick_sort_challenge.ipynb
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@ -34,9 +34,13 @@
"source": [ "source": [
"## Constraints\n", "## Constraints\n",
"\n", "\n",
"* Is a naiive solution sufficient (ie not in-place)?\n", "* Is a naive solution sufficient (ie not in-place)?\n",
" * Yes\n", " * Yes\n",
"* Are duplicates allowed?\n", "* Are duplicates allowed?\n",
" * Yes\n",
"* Can we assume the input is valid?\n",
" * No\n",
"* Can we assume this fits memory?\n",
" * Yes" " * Yes"
] ]
}, },
@ -46,7 +50,7 @@
"source": [ "source": [
"## Test Cases\n", "## Test Cases\n",
"\n", "\n",
"* None -> None\n", "* None -> Exception\n",
"* Empty input -> []\n", "* Empty input -> []\n",
"* One element -> [element]\n", "* One element -> [element]\n",
"* Two or more elements" "* Two or more elements"
@ -76,9 +80,11 @@
}, },
"outputs": [], "outputs": [],
"source": [ "source": [
"def quick_sort(data):\n", "class QuickSort(object):\n",
" # TODO: Implement me\n", "\n",
" pass" " def sort(self, data):\n",
" # TODO: Implement me\n",
" pass"
] ]
}, },
{ {
@ -101,37 +107,33 @@
"outputs": [], "outputs": [],
"source": [ "source": [
"# %load test_quick_sort.py\n", "# %load test_quick_sort.py\n",
"from nose.tools import assert_equal\n", "from nose.tools import assert_equal, assert_raises\n",
"\n", "\n",
"\n", "\n",
"class TestQuickSort(object):\n", "class TestQuickSort(object):\n",
" def test_quick_sort(self, func):\n", "\n",
" def test_quick_sort(self):\n",
" quick_sort = QuickSort()\n",
"\n",
" print('None input')\n", " print('None input')\n",
" data = None\n", " assert_raises(TypeError, quick_sort.sort, None)\n",
" sorted_data = func(data)\n",
" assert_equal(sorted_data, None)\n",
"\n", "\n",
" print('Empty input')\n", " print('Empty input')\n",
" data = []\n", " assert_equal(quick_sort.sort([]), [])\n",
" sorted_data = func(data)\n",
" assert_equal(sorted_data, [])\n",
"\n", "\n",
" print('One element')\n", " print('One element')\n",
" data = [5]\n", " assert_equal(quick_sort.sort([5]), [5])\n",
" sorted_data = func(data)\n",
" assert_equal(sorted_data, [5])\n",
"\n", "\n",
" print('Two or more elements')\n", " print('Two or more elements')\n",
" data = [5, 1, 7, 2, 6, -3, 5, 7, -1]\n", " data = [5, 1, 7, 2, 6, -3, 5, 7, -1]\n",
" sorted_data = func(data)\n", " assert_equal(quick_sort.sort(data), sorted(data))\n",
" assert_equal(sorted_data, sorted(data))\n",
"\n", "\n",
" print('Success: test_quick_sort\\n')\n", " print('Success: test_quick_sort\\n')\n",
"\n", "\n",
"\n", "\n",
"def main():\n", "def main():\n",
" test = TestQuickSort()\n", " test = TestQuickSort()\n",
" test.test_quick_sort(quick_sort)\n", " test.test_quick_sort()\n",
"\n", "\n",
"\n", "\n",
"if __name__ == '__main__':\n", "if __name__ == '__main__':\n",

88
sorting_searching/quick_sort/quick_sort_solution.ipynb
View File

@ -34,9 +34,13 @@
"source": [ "source": [
"## Constraints\n", "## Constraints\n",
"\n", "\n",
"* Is a naiive solution sufficient (ie not in-place)?\n", "* Is a naive solution sufficient (ie not in-place)?\n",
" * Yes\n", " * Yes\n",
"* Are duplicates allowed?\n", "* Are duplicates allowed?\n",
" * Yes\n",
"* Can we assume the input is valid?\n",
" * No\n",
"* Can we assume this fits memory?\n",
" * Yes" " * Yes"
] ]
}, },
@ -46,7 +50,7 @@
"source": [ "source": [
"## Test Cases\n", "## Test Cases\n",
"\n", "\n",
"* None -> None\n", "* None -> Exception\n",
"* Empty input -> []\n", "* Empty input -> []\n",
"* One element -> [element]\n", "* One element -> [element]\n",
"* Two or more elements" "* Two or more elements"
@ -74,7 +78,16 @@
"* 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+m), n = number of elements, m = recursion depth\n", "* Space: O(n+m), n = number of elements, m = recursion depth\n",
"\n", "\n",
"Most implementations are not stable." "Misc:\n",
"\n",
"* More sophisticated implementations are in-place, although they still take up recursion depth space\n",
"* Most implementations are not stable\n",
"\n",
"See [Quicksort on wikipedia](https://en.wikipedia.org/wiki/Quicksort):\n",
"\n",
"Typically, quicksort is significantly faster in practice than other Θ(nlogn) algorithms, because its inner loop can be efficiently implemented on most architectures [presumably because it has good cache locality], and in most real-world data, it is possible to make design choices which minimize the probability of requiring quadratic time.\n",
"\n",
"See: [Quicksort vs merge sort](http://stackoverflow.com/questions/70402/why-is-quicksort-better-than-mergesort)"
] ]
}, },
{ {
@ -95,28 +108,33 @@
"from __future__ import division\n", "from __future__ import division\n",
"\n", "\n",
"\n", "\n",
"def quick_sort(data):\n", "class QuickSort(object):\n",
" if data is None or len(data) < 2:\n",
" return data\n",
" equal = []\n",
" left = []\n",
" right = []\n",
" pivot_index = len(data) // 2\n",
" pivot_value = data[pivot_index]\n",
"\n", "\n",
" # Build the left and right partitions\n", " def sort(self, data):\n",
" for i in range(len(data)):\n", " if data is None:\n",
" if data[i] == pivot_value:\n", " raise TypeError('data cannot be None')\n",
" equal.append(data[i])\n", " return self._sort(data)\n",
" elif data[i] < pivot_value:\n",
" left.append(data[i])\n",
" else:\n",
" right.append(data[i])\n",
"\n", "\n",
" # Recursively apply quick_sort\n", " def _sort(self, data):\n",
" left = quick_sort(left)\n", " if len(data) < 2:\n",
" right = quick_sort(right)\n", " return data\n",
" return left + equal + right" " equal = []\n",
" left = []\n",
" right = []\n",
" pivot_index = len(data) // 2\n",
" pivot_value = data[pivot_index]\n",
" # Build the left and right partitions\n",
" for item in data:\n",
" if item == pivot_value:\n",
" equal.append(item)\n",
" elif item < pivot_value:\n",
" left.append(item)\n",
" else:\n",
" right.append(item)\n",
" # Recursively apply quick_sort\n",
" left_ = self._sort(left)\n",
" right_ = self._sort(right)\n",
" return left_ + equal + right_"
] ]
}, },
{ {
@ -144,37 +162,33 @@
], ],
"source": [ "source": [
"%%writefile test_quick_sort.py\n", "%%writefile test_quick_sort.py\n",
"from nose.tools import assert_equal\n", "from nose.tools import assert_equal, assert_raises\n",
"\n", "\n",
"\n", "\n",
"class TestQuickSort(object):\n", "class TestQuickSort(object):\n",
" def test_quick_sort(self, func):\n", "\n",
" def test_quick_sort(self):\n",
" quick_sort = QuickSort()\n",
"\n",
" print('None input')\n", " print('None input')\n",
" data = None\n", " assert_raises(TypeError, quick_sort.sort, None)\n",
" sorted_data = func(data)\n",
" assert_equal(sorted_data, None)\n",
"\n", "\n",
" print('Empty input')\n", " print('Empty input')\n",
" data = []\n", " assert_equal(quick_sort.sort([]), [])\n",
" sorted_data = func(data)\n",
" assert_equal(sorted_data, [])\n",
"\n", "\n",
" print('One element')\n", " print('One element')\n",
" data = [5]\n", " assert_equal(quick_sort.sort([5]), [5])\n",
" sorted_data = func(data)\n",
" assert_equal(sorted_data, [5])\n",
"\n", "\n",
" print('Two or more elements')\n", " print('Two or more elements')\n",
" data = [5, 1, 7, 2, 6, -3, 5, 7, -1]\n", " data = [5, 1, 7, 2, 6, -3, 5, 7, -1]\n",
" sorted_data = func(data)\n", " assert_equal(quick_sort.sort(data), sorted(data))\n",
" assert_equal(sorted_data, sorted(data))\n",
"\n", "\n",
" print('Success: test_quick_sort\\n')\n", " print('Success: test_quick_sort\\n')\n",
"\n", "\n",
"\n", "\n",
"def main():\n", "def main():\n",
" test = TestQuickSort()\n", " test = TestQuickSort()\n",
" test.test_quick_sort(quick_sort)\n", " test.test_quick_sort()\n",
"\n", "\n",
"\n", "\n",
"if __name__ == '__main__':\n", "if __name__ == '__main__':\n",

24
sorting_searching/quick_sort/test_quick_sort.py
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@ -1,34 +1,30 @@
from nose.tools import assert_equal from nose.tools import assert_equal, assert_raises
class TestQuickSort(object): class TestQuickSort(object):
def test_quick_sort(self, func):
def test_quick_sort(self):
quick_sort = QuickSort()
print('None input') print('None input')
data = None assert_raises(TypeError, quick_sort.sort, None)
sorted_data = func(data)
assert_equal(sorted_data, None)
print('Empty input') print('Empty input')
data = [] assert_equal(quick_sort.sort([]), [])
sorted_data = func(data)
assert_equal(sorted_data, [])
print('One element') print('One element')
data = [5] assert_equal(quick_sort.sort([5]), [5])
sorted_data = func(data)
assert_equal(sorted_data, [5])
print('Two or more elements') print('Two or more elements')
data = [5, 1, 7, 2, 6, -3, 5, 7, -1] data = [5, 1, 7, 2, 6, -3, 5, 7, -1]
sorted_data = func(data) assert_equal(quick_sort.sort(data), sorted(data))
assert_equal(sorted_data, sorted(data))
print('Success: test_quick_sort\n') print('Success: test_quick_sort\n')
def main(): def main():
test = TestQuickSort() test = TestQuickSort()
test.test_quick_sort(quick_sort) test.test_quick_sort()
if __name__ == '__main__': if __name__ == '__main__':