力扣-235题二叉搜索树的最近公共祖先（C++）- 牢记二叉搜索树的特性

清疚 2022-09-01 14:56 144阅读 0赞

题目链接：[https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-search-tree/][https_leetcode-cn.com_problems_lowest-common-ancestor-of-a-binary-search-tree]  
题目如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 1]

/**
     * 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==NULL) return NULL;
            //公共祖先：即根节点大于左节点，小于右节点
    
            if(p->val < root->val&&q->val < root->val)//当前节点大于左右节点
                return lowestCommonAncestor(root->left,p,q);
    
            if(p->val > root->val&&q->val > root->val)//当前节点小于左右节点
                return lowestCommonAncestor(root->right,p,q);
    
            return root;
        }
    };

[https_leetcode-cn.com_problems_lowest-common-ancestor-of-a-binary-search-tree]: https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-search-tree/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]: /images/20220829/8abad3f596a44890b966eac19b9820ea.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 1]: /images/20220829/2f3696220ece441d86b8a316cc9e6216.png