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Merge pull request #65 from donnemartin/develop

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Polish selection sort challenge and solution
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Donne Martin 2016-06-18 22:12:49 -04:00 committed by GitHub
commit e22ee5fbe2
3 changed files with 19 additions and 9 deletions
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6
sorting_searching/selection_sort/selection_sort_challenge.ipynb
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@ -35,6 +35,8 @@
"## Constraints\n", "## Constraints\n",
"\n", "\n",
"* Is a naiive solution sufficient (ie not stable, not based on a heap)?\n", "* Is a naiive solution sufficient (ie not stable, not based on a heap)?\n",
" * Yes\n",
"* Are duplicates allowed?\n",
" * Yes" " * Yes"
] ]
}, },
@ -134,7 +136,7 @@
" assert_equal(data, [5])\n", " assert_equal(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, -10]\n",
" func(data)\n", " func(data)\n",
" assert_equal(data, sorted(data))\n", " assert_equal(data, sorted(data))\n",
"\n", "\n",
@ -183,7 +185,7 @@
"name": "python", "name": "python",
"nbconvert_exporter": "python", "nbconvert_exporter": "python",
"pygments_lexer": "ipython3", "pygments_lexer": "ipython3",
"version": "3.4.3" "version": "3.5.0"
} }
}, },
"nbformat": 4, "nbformat": 4,

20
sorting_searching/selection_sort/selection_sort_solution.ipynb
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@ -34,6 +34,8 @@
"## Constraints\n", "## Constraints\n",
"\n", "\n",
"* Is a naiive solution sufficient (ie not stable, not based on a heap)?\n", "* Is a naiive solution sufficient (ie not stable, not based on a heap)?\n",
" * Yes\n",
"* Are duplicates allowed?\n",
" * Yes" " * Yes"
] ]
}, },
@ -66,7 +68,7 @@
"\n", "\n",
"Complexity:\n", "Complexity:\n",
"* Time: O(n^2) average, worst, best\n", "* Time: O(n^2) average, worst, best\n",
"* Space: O(1) iterative, O(n) recursive (unless tail-call elimination is available, then O(1)), generally not stable\n", "* Space: O(1) iterative, O(m) recursive where m is the recursion depth (unless tail-call elimination is available, then O(1)), generally not stable\n",
" * Note: Tail call elimination is not inherently available in Python. See the following [StackOverflow post](http://stackoverflow.com/a/13592002)." " * Note: Tail call elimination is not inherently available in Python. See the following [StackOverflow post](http://stackoverflow.com/a/13592002)."
] ]
}, },
@ -112,6 +114,9 @@
"outputs": [], "outputs": [],
"source": [ "source": [
"def find_min_index(data, start):\n", "def find_min_index(data, start):\n",
" # Raises an exception if: \n",
" # -data is None\n",
" # -start >= len(data) - 1\n",
" min_index = start\n", " min_index = start\n",
" for i in range(start + 1, len(data)):\n", " for i in range(start + 1, len(data)):\n",
" if data[i] < data[min_index]:\n", " if data[i] < data[min_index]:\n",
@ -120,13 +125,16 @@
"\n", "\n",
"\n", "\n",
"def swap(data, i, j):\n", "def swap(data, i, j):\n",
" if (i != j):\n", " # Raises an exception if: \n",
" # -data is None\n",
" # -i or j are >= len(data)\n",
" if i != j:\n",
" data[i], data[j] = data[j], data[i]\n", " data[i], data[j] = data[j], data[i]\n",
"\n", "\n",
"\n", "\n",
"def selection_sort_recursive(data, start=0):\n", "def selection_sort_recursive(data, start=0):\n",
" if data is None:\n", " if data is None:\n",
" return None\n", " return\n",
" if start < len(data) - 1:\n", " if start < len(data) - 1:\n",
" swap(data, start, find_min_index(data, start))\n", " swap(data, start, find_min_index(data, start))\n",
" selection_sort_recursive(data, start+1)\n", " selection_sort_recursive(data, start+1)\n",
@ -135,7 +143,7 @@
"def selection_sort_iterative_alt(data):\n", "def selection_sort_iterative_alt(data):\n",
" if data is None or len(data) < 2:\n", " if data is None or len(data) < 2:\n",
" return\n", " return\n",
" for i in range(0, len(data) - 1):\n", " for i in range(len(data)-1):\n",
" swap(data, i, find_min_index(data, i))" " swap(data, i, find_min_index(data, i))"
] ]
}, },
@ -186,7 +194,7 @@
" assert_equal(data, [5])\n", " assert_equal(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, -10]\n",
" func(data)\n", " func(data)\n",
" assert_equal(data, sorted(data))\n", " assert_equal(data, sorted(data))\n",
"\n", "\n",
@ -262,7 +270,7 @@
"name": "python", "name": "python",
"nbconvert_exporter": "python", "nbconvert_exporter": "python",
"pygments_lexer": "ipython3", "pygments_lexer": "ipython3",
"version": "3.4.3" "version": "3.5.0"
} }
}, },
"nbformat": 4, "nbformat": 4,

2
sorting_searching/selection_sort/test_selection_sort.py
View File

@ -20,7 +20,7 @@ class TestSelectionSort(object):
assert_equal(data, [5]) assert_equal(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, -10]
func(data) func(data)
assert_equal(data, sorted(data)) assert_equal(data, sorted(data))