119. Pascal's Triangle II.ipynb

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    "Given an index k, return the kth row of the Pascal's triangle.\n",
    "\n",
    "For example, given k = 3,\n",
    "Return [1,3,3,1].\n",
    "\n",
    "Note:\n",
    "Could you optimize your algorithm to use only O(k) extra space?"
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    "class Solution(object):\n",
    "    def getRow(self, rowIndex):\n",
    "        \"\"\"\n",
    "        :type rowIndex: int\n",
    "        :rtype: List[int]\n",
    "        \"\"\"\n",
    "        if rowIndex<0:\n",
    "            return []\n",
    "        if rowIndex==0:\n",
    "            return [1]\n",
    "        if rowIndex==1:\n",
    "            return [1,1]\n",
    "        preRow=[1,1]\n",
    "        for i in range(2,rowIndex+1):\n",
    "            res=[1]\n",
    "            for j in range(i-1):\n",
    "                res.append(preRow[j]+preRow[j+1])\n",
    "            res.append(1)\n",
    "            preRow=res\n",
    "        return res\n",
    "        "
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    "s=Solution()"
   ]
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       "[1, 3, 3, 1]"
      ]
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     "execution_count": 16,
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    "s.getRow(3)"
   ]
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