lowest-common-ancestor-of-a-binary-search-tree

Lowest Common Ancestor of a Binary Search Tree – LeetCode 235

Problem

Description

Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.

Answer

Original

Code

/**
 * 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->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;
    }
};

思路

使用BFS判断，得益于BST的大小关系可以直接搜索，时间复杂度$O(n)$，空间复杂度$O(1)$。
耗时$22$ ms，排名$5.84\%$

Better

思路

还没看到更好的思路。