108. Convert Sorted Array to Binary Search Tree.ipynb

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   "source": [
    "Given an array where elements are sorted in ascending order, convert it to a height balanced BST."
   ]
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   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
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    "class TreeNode(object):\n",
    "    def __init__(self,x):\n",
    "        self.val=x\n",
    "        self.left=None\n",
    "        self.right=None\n",
    "class Solution(object):\n",
    "    def sortedArrayToBST(self, nums):\n",
    "        \"\"\"\n",
    "        :type nums: List[int]\n",
    "        :rtype: TreeNode\n",
    "        \"\"\"\n",
    "        if not nums or len(nums)==0:\n",
    "            return None\n",
    "        if len(nums)==1:\n",
    "            return TreeNode(nums[0])\n",
    "        mid=len(nums)//2\n",
    "        root=TreeNode(nums[mid])\n",
    "        root.left=self.sortedArrayToBST(nums[:mid])\n",
    "        root.right=self.sortedArrayToBST(nums[mid+1:])\n",
    "        return root\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": true
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   "outputs": [],
   "source": [
    "s=Solution()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
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   "outputs": [
    {
     "name": "stdout",
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     "text": [
      "1 2\n"
     ]
    }
   ],
   "source": [
    "root=s.sortedArrayToBST([1,2])\n",
    "print(root.left.val,root.val)"
   ]
  },
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   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
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   "source": [
    "sf=[1,2]"
   ]
  },
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   "cell_type": "code",
   "execution_count": 6,
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    {
     "ename": "TypeError",
     "evalue": "object of type 'NoneType' has no len()",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-6-48ab06a8724d>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mlen\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;32mNone\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mTypeError\u001b[0m: object of type 'NoneType' has no len()"
     ]
    }
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   "source": [
    "len(None)"
   ]
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   "outputs": [],
   "source": [
    "[1,2,3,4,5]"
   ]
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   "source": [
    "[3,]"
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