quicksort_sample_CSS.ipynb

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   "source": [
    "from random import randrange\n",
    "from random import sample\n",
    "\n",
    "# given list, sub-list (defined by start and end indices), random pivot index\n",
    "def partition(lst, start, end, pivot):\n",
    "    # place pivot at the end of the sub-list\n",
    "    lst[pivot], lst[end] = lst[end], lst[pivot]\n",
    "    lst_below_pivot = []\n",
    "    lst_above_pivot = []\n",
    "    query_counter = 0 \n",
    "    \n",
    "    # dividing into two lists (above and below pivot)\n",
    "    for i in range(start, end):\n",
    "        query_counter +=1 \n",
    "        if lst[i] < lst[end]:\n",
    "              lst_below_pivot.append(lst[i])\n",
    "        if lst[i] >= lst[end]:\n",
    "              lst_above_pivot.append(lst[i])\n",
    "    \n",
    "    next_pivot = start + len(lst_below_pivot)\n",
    "    \n",
    "    lst[start : next_pivot ] = lst_below_pivot\n",
    "    lst[next_pivot] = lst[end]\n",
    "    lst[(next_pivot + 1): end+1 ] = lst_above_pivot\n",
    "\n",
    "    return next_pivot, query_counter\n",
    "\n",
    "def quick_sort(lst, start, end):\n",
    "    if start >= end:\n",
    "        return 0\n",
    "    pivot = randrange(start, end + 1)\n",
    "    new_pivot, nqueries = partition(lst, start, end, pivot)\n",
    "    nqueries += quick_sort(lst, start, new_pivot - 1)\n",
    "    nqueries += quick_sort(lst, new_pivot + 1, end)\n",
    "    return nqueries\n",
    "\n",
    "def sort(lst):\n",
    "    nqueries = quick_sort(lst, 0, len(lst) - 1)\n",
    "    return nqueries\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
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   "source": [
    "from copy import deepcopy\n",
    "\n",
    "lst = sample( range(1000), 100)\n",
    "lstcopy = deepcopy(lst)\n",
    "total_queries = sort(lst)  \n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "print \"original list:\" , lstcopy , \"\\n\" \n",
    "print \"sorted list:\", lst , \"\\n\\n\" \n",
    "\n",
    "print \"total number of items = \" , len(lst)\n",
    "print \"total non-adaptive queries required = n(n-1)/2 = \" , len(lst)*(len(lst)-1)/2\n",
    "print \"total quicksort queries = \" , total_queries\n",
    "     "
   ]
  }
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