list_shuffle.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "import copy\n",
    "import random"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "def shuffle(x):\n",
    "    data = copy.deepcopy(x)\n",
    "    for hi in range(len(data)-1, -1, -1):\n",
    "        idx = random.randint(0, hi)\n",
    "        # Swap value at idx and at hi\n",
    "        # We store the shuffled data at the end (hi),\n",
    "        # and then keep shuffling the remainder (0, hi-1)\n",
    "        data[hi], data[idx] = data[idx], data[hi]\n",
    "    return data"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [],
   "source": [
    "data = list(range(20))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]\n",
      "[5, 17, 6, 16, 0, 18, 11, 9, 4, 8, 1, 14, 19, 13, 12, 2, 3, 10, 15, 7]\n"
     ]
    }
   ],
   "source": [
    "shuffled = shuffle(data)\n",
    "print(data)\n",
    "print(shuffled)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Check that there is no replacement\n",
    "# The original data can have replacement also,\n",
    "# so we need to make sure we have the same counts\n",
    "# of each item.\n",
    "\n",
    "def validate_shuffle(orig_data, shuffled_data):\n",
    "    for orig, shuffled in zip(sorted(orig_data), sorted(shuffled_data)):\n",
    "        if orig != shuffled:\n",
    "            return False\n",
    "    return True"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "validate_shuffle(data, shuffled)"
   ]
  }
 ],
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