quicksort from

quicksort.ipynb

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  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The Quick Sort with a different two finger partition alorithn from Problem Solving with Algorithms and Data Structures see at http://interactivepython.org/ http://interactivepython.org/runestone/static/pythonds/SortSearch/TheQuickSort.html"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": true
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   "outputs": [],
   "source": [
    "def quickSort(alist):\n",
    "   quickSortHelper(alist,0,len(alist)-1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": true
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   "source": [
    "def quickSortHelper(alist,first,last):\n",
    "   if first<last:\n",
    "\n",
    "       splitpoint = partition(alist,first,last)\n",
    "\n",
    "       quickSortHelper(alist,first,splitpoint-1)\n",
    "       quickSortHelper(alist,splitpoint+1,last)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def partition(alist,first,last):\n",
    "   pivotvalue = alist[first]\n",
    "\n",
    "   leftmark = first+1\n",
    "   rightmark = last\n",
    "\n",
    "   done = False\n",
    "   while not done:\n",
    "\n",
    "       while leftmark <= rightmark and alist[leftmark] <= pivotvalue:\n",
    "           leftmark = leftmark + 1\n",
    "\n",
    "       while alist[rightmark] >= pivotvalue and rightmark >= leftmark:\n",
    "           rightmark = rightmark -1\n",
    "\n",
    "       if rightmark < leftmark:\n",
    "           done = True\n",
    "       else:\n",
    "           temp = alist[leftmark]\n",
    "           alist[leftmark] = alist[rightmark]\n",
    "           alist[rightmark] = temp\n",
    "\n",
    "   temp = alist[first]\n",
    "   alist[first] = alist[rightmark]\n",
    "   alist[rightmark] = temp\n",
    "\n",
    "\n",
    "   return rightmark"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[17, 20, 26, 31, 44, 54, 55, 77, 93]\n",
      "[11, 17, 20, 26, 31, 44, 54, 55, 73, 77, 93]\n"
     ]
    }
   ],
   "source": [
    "alist = [54,26,93,17,77,31,44,55,20]\n",
    "quickSort(alist)\n",
    "print(alist)\n",
    "alist = [73,54,26,93,17,77,31,44,55,20,11]\n",
    "quickSort(alist)\n",
    "print(alist)"
   ]
  }
 ],
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