{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Radix Sort\n",
    "© 2021, Joe James"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [],
   "source": [
    "# flatten into a 1D List\n",
    "from functools import reduce\n",
    "def flatten(A):\n",
    "    return reduce(lambda x, y: x + y, A)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 34,
   "metadata": {},
   "outputs": [],
   "source": [
    "def radix_sort(A):\n",
    "    # get number of digits in largest item\n",
    "    num_digits = len(str(max(A)))\n",
    "    for digit in range(0, num_digits):\n",
    "        B = [[] for i in range(10)]\n",
    "        e = 10 ** digit\n",
    "        for item in A:\n",
    "            # num is the bucket number that the item will be put into\n",
    "            num = item // e % 10\n",
    "            B[num].append(item)\n",
    "        A = flatten(B)\n",
    "    return A"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Test Function\n",
    "Set a result flag. The j loop is used to perform 1000 test iterations. The next two lines create and shuffle list A of 100 integers. Then A is passed to our sorting function. The sorted result is compared to a sort using Python's sorted function. After 1000 iterations of the test, the result is printed.  \n",
    "Note that Radix is not in-place, so we need to assign the returned list to A, A = func(A)\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 35,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Success\n"
     ]
    }
   ],
   "source": [
    "import random\n",
    "\n",
    "def test(func):\n",
    "    result = 'Success'\n",
    "    for j in range(1000):\n",
    "        A = [k for k in range(100)]\n",
    "        random.shuffle(A)\n",
    "        A = func(A)\n",
    "        if A != sorted(A):\n",
    "            result = 'Failed'\n",
    "    print(result)\n",
    "test(radix_sort)"
   ]
  },
  {
   "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
}