235. Lowest Common Ancestor of a Binary Search Tree.ipynb

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    "Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.\n",
    "\n",
    "According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).”\n",
    "\n",
    "        _______6______\n",
    "       /              \\\n",
    "    ___2__          ___8__\n",
    "   /      \\        /      \\\n",
    "   0      _4       7       9\n",
    "         /  \\\n",
    "         3   5\n",
    "For example, the lowest common ancestor (LCA) of nodes 2 and 8 is 6. Another example is LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition."
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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",
    "        \n",
    "class Solution(object):\n",
    "    def lowestCommonAncestor(self, root, p, q):\n",
    "        \"\"\"\n",
    "        :type root: TreeNode\n",
    "        :type p: TreeNode\n",
    "        :type q: TreeNode\n",
    "        :rtype: TreeNode\n",
    "        \"\"\"\n",
    "        while (root.val-p.val)*(root.val-q.val)>0:\n",
    "            root=(root.left,root.right)[p.val>root.val]\n",
    "        return root"
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