LeetCode-236.Lowest Common Ancestor of a Binary Tree
Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.
According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself).”
Given the following binary tree: root = [3,5,1,6,2,0,8,null,null,7,4]
Example 1:
Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1
Output: 3
Explanation: The LCA of nodes 5 and 1 is 3.
Example 2:
Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4 Output: 5 Explanation: The LCA of nodes 5 and 4 is 5, since a node can be a descendant of itself according to the LCA definition.
Note:
- All of the nodes' values will be unique.
- p and q are different and both values will exist in the binary tree.
可查找两个结点,并记录各自的路径,随时间复杂度也是O(n),但较复杂
下面解法,时间复杂度O(n)
1 public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {//树 递归 mytip 2 if (null==root||root.val==p.val||root.val==q.val){ 3 return root; 4 } 5 TreeNode left = lowestCommonAncestor(root.left,p,q); 6 TreeNode right = lowestCommonAncestor(root.right,p,q); 7 if(null!=left&&null!=right){ 8 return root; 9 } 10 else if (null ==right){ 11 return left; 12 } 13 else{ 14 return right; 15 } 16 }
相关题
LeetCode235 二叉搜索树的最近公共祖先 https://www.cnblogs.com/zhacai/p/10592518.html
【推荐】编程新体验,更懂你的AI,立即体验豆包MarsCode编程助手
【推荐】凌霞软件回馈社区,博客园 & 1Panel & Halo 联合会员上线
【推荐】抖音旗下AI助手豆包,你的智能百科全书,全免费不限次数
【推荐】轻量又高性能的 SSH 工具 IShell:AI 加持,快人一步
· 深入理解 Mybatis 分库分表执行原理
· 如何打造一个高并发系统?
· .NET Core GC压缩(compact_phase)底层原理浅谈
· 现代计算机视觉入门之:什么是图片特征编码
· .NET 9 new features-C#13新的锁类型和语义
· Spring AI + Ollama 实现 deepseek-r1 的API服务和调用
· 《HelloGitHub》第 106 期
· 数据库服务器 SQL Server 版本升级公告
· 深入理解Mybatis分库分表执行原理
· 使用 Dify + LLM 构建精确任务处理应用