Revised QuickSort code, in Jupyter nb

Sorting Algorithms/Python QuickSort.ipynb

@@ -0,0 +1,140 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Python QuickSort Algorithm"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[5, 9, 1, 2, 4, 8, 6, 3, 7]\n",
+      "[1, 2, 3, 4, 5, 6, 7, 8, 9]\n"
+     ]
+    }
+   ],
+   "source": [
+    "#---------------------------------------\n",
+    "# Quick Sort\n",
+    "#---------------------------------------\n",
+    "def quick_sort(A):\n",
+    "    quick_sort2(A, 0, len(A)-1)\n",
+    "    \n",
+    "def quick_sort2(A, low, hi):\n",
+    "    if hi-low < 1 and low < hi:\n",
+    "        quick_selection(A, low, hi)\n",
+    "    elif low < hi:\n",
+    "        p = partition(A, low, hi)\n",
+    "        quick_sort2(A, low, p - 1)\n",
+    "        quick_sort2(A, p + 1, hi)\n",
+    "    \n",
+    "def get_pivot(A, low, hi):\n",
+    "    mid = (hi + low) // 2\n",
+    "    s = sorted([A[low], A[mid], A[hi]])\n",
+    "    if s[1] == A[low]:\n",
+    "        return low\n",
+    "    elif s[1] == A[mid]:\n",
+    "        return mid\n",
+    "    return hi\n",
+    "    \n",
+    "def partition(A, low, hi):\n",
+    "    pivotIndex = get_pivot(A, low, hi)\n",
+    "    pivotValue = A[pivotIndex]\n",
+    "    A[pivotIndex], A[low] = A[low], A[pivotIndex]\n",
+    "    border = low\n",
+    "\n",
+    "    for i in range(low, hi+1):\n",
+    "        if A[i] < pivotValue:\n",
+    "            border += 1\n",
+    "            A[i], A[border] = A[border], A[i]\n",
+    "    A[low], A[border] = A[border], A[low]\n",
+    "\n",
+    "    return (border)\n",
+    "    \n",
+    "def quick_selection(x, first, last):\n",
+    "    for i in range (first, last):\n",
+    "        minIndex = i\n",
+    "        for j in range (i+1, last+1):\n",
+    "            if x[j] < x[minIndex]:\n",
+    "                minIndex = j\n",
+    "        if minIndex != i:\n",
+    "            x[i], x[minIndex] = x[minIndex], x[i]\n",
+    "            \n",
+    "A = [5,9,1,2,4,8,6,3,7]\n",
+    "print(A)\n",
+    "quick_sort(A)\n",
+    "print(A)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Nice simple version written by Mr. UncleChu in comments\n",
+    "Slick code, but does not sort in place, so uses a lot more memory. Do not use for large lists or you'll get stackoverflow."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[5, 9, 1, 2, 4, 8, 6, 3, 7]\n",
+      "[1, 2, 3, 4, 5, 6, 7, 8, 9]\n"
+     ]
+    }
+   ],
+   "source": [
+    "def quick_sort_chu(a_list):\n",
+    "    if len(a_list) < 2: return a_list\n",
+    "    lesser = quick_sort([x for x in a_list[1:] if x <= a_list[0]])\n",
+    "    bigger = quick_sort([x for x in a_list[1:] if x > a_list[0]])\n",
+    "    return sum([lesser, [a_list[0]], bigger], [])\n",
+    "A = [5,9,1,2,4,8,6,3,7]\n",
+    "print(A)\n",
+    "B = quick_sort_chu(A)\n",
+    "print(B)"
+   ]
+  },
+  {
+   "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": 2
+}