Add Heap sort

sorting_searching/heap_sort/heap_sort_solution.ipynb

@@ -0,0 +1,240 @@
+{
+ "cells": [
+  {
+   "cell_type": "raw",
+   "metadata": {},
+   "source": [
+    "This notebook was prepared by [Donne Martin](http://donnemartin.com). 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 heap sort.\n",
+    "\n",
+    "* [Constraints](#Constraints)\n",
+    "* [Test Cases](#Test-Cases)\n",
+    "* [Algorithm](#Algorithm)\n",
+    "* [Code](#Code)\n",
+    "* [Pythonic-Code](#Pythonic-Code)\n",
+    "* [Unit Test](#Unit-Test)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Constraints\n",
+    "\n",
+    "* Is a naive solution sufficient?\n",
+    "    * Yes\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"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test Cases\n",
+    "\n",
+    "* None -> Exception\n",
+    "* Empty input -> []\n",
+    "* One element -> [element]\n",
+    "* Two or more elements"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Algorithm\n",
+    "\n",
+    "Wikipedia's animation:\n",
+    "![alt text](https://upload.wikimedia.org/wikipedia/commons/1/1b/Sorting_heapsort_anim.gif)\n",
+    "\n",
+    "* Convert a given list to a max-heap\n",
+    "* For i from n-1 to 0 (n is size of a given list) :\n",
+    "    * Swap 0-th element with i-th element\n",
+    "    * Heapfiy a sub-list(0 ~ i-1)\n",
+    "\n",
+    "Complexity:\n",
+    "* Time: O(n log(n)) average, best, worst\n",
+    "* Space: O(n)\n",
+    "    * This implementation is in-place sort, so it needs no additional space.\n",
+    "\n",
+    "Misc:\n",
+    "\n",
+    "* Most implementations are not stable\n",
+    "\n",
+    "See [Heapsort on wikipedia](https://en.wikipedia.org/wiki/Heapsort):\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Code"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from __future__ import division\n",
+    "\n",
+    "\n",
+    "class HeapSort(object):\n",
+    "    \n",
+    "    def heapify(self, data, n, root):\n",
+    "        while (2*root + 1 < n):\n",
+    "            ch = 2 * root + 1\n",
+    "            if ch+1 < n and data[ch] < data[ch+1]:\n",
+    "                ch += 1\n",
+    "            if data[ch] < data[root]:\n",
+    "                break\n",
+    "            data[ch], data[root] = data[root], data[ch]\n",
+    "            root = ch\n",
+    "\n",
+    "    def sort(self, data):\n",
+    "        if data is None:\n",
+    "            raise TypeError('data cannot be None')\n",
+    "        return self._sort(data)\n",
+    "\n",
+    "    def _sort(self, data):\n",
+    "        n = len(data)\n",
+    "        if n < 2:\n",
+    "            return data\n",
+    "        for i in range(n//2 - 1, -1, -1):\n",
+    "            self.heapify(data, n, i)\n",
+    "        \n",
+    "        # extract elements\n",
+    "        for i in range(n-1, 0, -1):\n",
+    "            data[i], data[0] = data[0], data[1]\n",
+    "            self.heapify(data, i, 0)\n",
+    "        return data  # return sorted array in ascending order\n",
+    "            "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unit Test\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 8,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Overwriting test_heap_sort.py\n"
+     ]
+    }
+   ],
+   "source": [
+    "%%writefile test_heap_sort.py\n",
+    "from nose.tools import assert_equal, assert_raises\n",
+    "\n",
+    "\n",
+    "class TestHeapSort(object):\n",
+    "\n",
+    "    def test_heap_sort(self):\n",
+    "        sort = HeapSort()\n",
+    "\n",
+    "        print('None input')\n",
+    "        assert_raises(TypeError, sort.sort, None)\n",
+    "\n",
+    "        print('Empty input')\n",
+    "        assert_equal(sort.sort([]), [])\n",
+    "\n",
+    "        print('One element')\n",
+    "        assert_equal(sort.sort([5]), [5])\n",
+    "\n",
+    "        print('Two or more elements')\n",
+    "        data = [5, 1, 7, 2, 6, -3, 5, 7, -1]\n",
+    "        assert_equal(sort.sort(data), sorted(data))\n",
+    "\n",
+    "        print('Success: test_heap_sort\\n')\n",
+    "\n",
+    "\n",
+    "def main():\n",
+    "    test = TestHeapSort()\n",
+    "    test.test_heap_sort()\n",
+    "\n",
+    "\n",
+    "if __name__ == '__main__':\n",
+    "    main()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 9,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "None input\n",
+      "Empty input\n",
+      "One element\n",
+      "Two or more elements\n",
+      "Success: test_heap_sort\n",
+      "\n"
+     ]
+    }
+   ],
+   "source": [
+    "%run -i test_heap_sort.py"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "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": "3.7.0"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 1
+}

sorting_searching/heap_sort/test_heap_sort.py

@@ -0,0 +1,31 @@
+from nose.tools import assert_equal, assert_raises
+
+
+class TestHeapSort(object):
+
+    def test_heap_sort(self):
+        sort = HeapSort()
+
+        print('None input')
+        assert_raises(TypeError, sort.sort, None)
+
+        print('Empty input')
+        assert_equal(sort.sort([]), [])
+
+        print('One element')
+        assert_equal(sort.sort([5]), [5])
+
+        print('Two or more elements')
+        data = [5, 1, 7, 2, 6, -3, 5, 7, -1]
+        assert_equal(sort.sort(data), sorted(data))
+
+        print('Success: test_heap_sort\n')
+
+
+def main():
+    test = TestHeapSort()
+    test.test_heap_sort()
+
+
+if __name__ == '__main__':
+    main()