stretch-shuffle.ipynb

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   "source": [
    "import numpy as np\n",
    "import random"
   ]
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     "execution_count": 32,
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   "source": [
    "albums = [random.randrange(5, 15) for _ in xrange(4)]\n",
    "albums"
   ]
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       "        [0, 0, 3, 0],\n",
       "        [0, 0, 0, 0]]),\n",
       " array([1, 1, 1, 1, 2, 1, 2, 4, 1, 4, 2, 4, 4, 2, 4, 2, 4, 4, 2, 4, 2, 4, 2,\n",
       "        4, 3, 4, 2, 3, 4, 3, 4, 2, 3, 3, 3, 3]))"
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   "source": [
    "def stretch_shuffle(albums):\n",
    "    space = max(albums) * 2\n",
    "    mat = np.zeros((space, len(albums)), dtype=int)\n",
    "    for e, album in enumerate(albums, start=1):\n",
    "        start = random.randrange(space - album)\n",
    "        stop = random.randrange(start + album, space)\n",
    "        step = float(stop - start) / album\n",
    "        indices = np.arange(start, stop, step).astype(int)\n",
    "        assert len(indices) == len(set(indices)) == album\n",
    "        mat[indices,e - 1] = e\n",
    "    flat = mat.reshape(-1)\n",
    "    return mat, flat[flat > 0]\n",
    "\n",
    "stretch_shuffle(albums)"
   ]
  },
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