235. Lowest Common Ancestor of a Binary Search Tree

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本文介绍了一个LeetCode上的题目，即如何在给定的二叉搜索树中找到两个节点的最近公共祖先。文章提供了详细的解决方案，并利用二叉搜索树的特性来进行高效的查找。

题目来源【Leetcode】

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).”
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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.

这道题是找两个结点最近的公共祖先，直接根据BST的性质进行分类即可：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        if(!root || p == root || q == root) return root;
        if(p->val < root->val && q->val < root->val) return lowestCommonAncestor(root->left, p, q);
        if(p->val > root->val && q->val > root->val) return lowestCommonAncestor(root->right, p, q);
        return root;
    }
};