235. Lowest Common Ancestor of a Binary Search Tree

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本文介绍了一种在二叉搜索树中寻找两个指定节点的最低公共祖先的方法。通过递归地比较节点值，算法有效地定位了目标节点的共同祖先。

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问题描述：
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).”

这里写图片描述

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.

java代码：

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {

        if(root.val>p.val && root.val>q.val)
            return lowestCommonAncestor(root.left,p,q);
        if(root.val<p.val && root.val<q.val)
            return lowestCommonAncestor(root.right,p,q);

        return root;
    }
}