2016-09-20 solution with @satabdidas

Week6.ipynb

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   "source": [
    "import itertools\n",
    "i = 0\n",
    "def counter():\n",
    "    global i\n",
    "    i += 1\n",
    "    return i\n",
    "\n",
    "# print(list(itertools.permutations('0123', 4)))\n",
    "''.join(next(itertools.dropwhile(lambda _: counter() < 1000000, itertools.permutations('0123456789', 10))))"
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     "text": [
      "ls ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']\n",
      "remainder 1000000\n",
      "index 2\n",
      "ls ['0', '1', '3', '4', '5', '6', '7', '8', '9']\n",
      "remainder 274240\n",
      "index 6\n",
      "ls ['0', '1', '3', '4', '5', '6', '8', '9']\n",
      "remainder 32320\n",
      "index 6\n",
      "ls ['0', '1', '3', '4', '5', '6', '9']\n",
      "remainder 2080\n",
      "index 2\n",
      "ls ['0', '1', '4', '5', '6', '9']\n",
      "remainder 640\n",
      "index 5\n",
      "ls ['0', '1', '4', '5', '6']\n",
      "remainder 40\n",
      "index 1\n",
      "ls ['0', '4', '5', '6']\n",
      "remainder 16\n",
      "index 2\n",
      "ls ['0', '4', '6']\n",
      "remainder 4\n",
      "index 2\n",
      "ls ['0', '4']\n",
      "remainder 0\n",
      "index 0\n"
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   "source": [
    "def fact(n):\n",
    "    if n == 1:\n",
    "        return 1\n",
    "    return n * fact(n - 1)\n",
    "\n",
    "def permutation_at(number):\n",
    "    ls = list('0123456789')\n",
    "    output = []\n",
    "    remainder = number\n",
    "    n = 9\n",
    "    while n > 0:\n",
    "        index = remainder // fact(n)\n",
    "        print('ls', ls)\n",
    "        print('remainder', remainder)\n",
    "        print('index', index)\n",
    "        \n",
    "        remainder = remainder % fact(n)\n",
    "        n -= 1\n",
    "        output.append(ls[index])\n",
    "        del ls[index]\n",
    "    return ''.join(output)\n",
    "permutation_at(1000000) "
   ]
  }
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