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Problem Definition:
Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.
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).”
思路：由根节点开始：
1) 如果根节点的值等于其中一个节点，则根节点就是要找的最低公共祖先，返回它；
2) 排序，确保p<=q;
3) 如果根节点值大于p而小于q，则p和q分别在根节点的左右子树，根节点就是要找的最低公共祖先，返回它；
4) 如果根节点值大于较大的q，则p和q都在根节点的左子树，令根节点左子节点为新的根节点；如果根节点值小于较小的p，则p和q都在根节点的右子树
另根节点右子节点为新的根节点；
5)递归地进行1)-->4).
代码：
# Definition for a binary tree node. # class TreeNode: # def __init__(self, x): # self.val = x # self.left = None # self.right = None class Solution: # @param {TreeNode} root # @param {TreeNode} p # @param {TreeNode} q # @return {TreeNode} def lowestCommonAncestor(self, root, p, q): if (root.val==p.val) or (root.val==q.val): return root if p.val>q.val: p,q=q,p if p.val<root.val and root.val<q.val: return root if root.val>q.val: root=root.left if root.val<p.val: root=root.right if root!=None: return self.lowestCommonAncestor(root, p, q)
LeetCode#235 Lowest Common Ancestor of a Binary Search Tree
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原文地址：http://www.cnblogs.com/acetseng/p/4648741.html
