Leetcode 235. Lowest Common Ancestor of a Binary Search Tree
Leetcode 235. Lowest Common Ancestor of a Binary Search Tree
triplebee
发布于 2018-01-12 14:43:23
发布于 2018-01-12 14:43:23
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).”
_______6______
/ \
___2__ ___8__
/ \ / \
0 _4 7 9
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3 5 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.
在二叉搜索树上找出两个点的LCA，最近公共祖先。
LCA的算法不唯一，但这里可以运用BST的性质进行搜索，如果p和q在root的一侧，则可以向那一侧搜索，否则root必定为两者的LCA。
/**
* 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) return NULL;
while((root->val - p->val) * (root->val - q->val) > 0)
root = root->val > p->val ? root->left : root->right;
return root;
}
};本文参与 腾讯云自媒体分享计划，分享自作者个人站点/博客。
原始发表：2017-04-06 ，如有侵权请联系 cloudcommunity@tencent.com 删除
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