【刷题-LeetCode】236. Lowest Common Ancestor of a Binary Tree
2024-10-19 21:21:42
- 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.
解 对于root节点,如果左右子树分别有一个节点,则root是一个公共祖先
解1 递归
class Solution {
public:
TreeNode *ans;
TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
LCA(root, p, q);
return ans;
}
bool LCA(TreeNode *root, TreeNode *p, TreeNode *q){
if(root == NULL)return false;
int l = LCA(root->left, p, q) ? 1 : 0; // p或者q在左子树
int r = LCA(root->right, p, q) ? 1 : 0; // p或者q在右子树
int mid = (root == p || root == q) ? 1 : 0; //找到了p或者q
if(mid + l + r >= 2)ans = root; // =2时,左右各一个;>2时,一个是另一个的先驱节点
return mid + l + r > 0; // >0表明找到了p或者q
}
};
最新文章
- 安装Mysql提示1045错误解决方法
- HDU 5791 Two DP
- JavaScript读二进制文件并用ajax传输二进制流
- NET MVC1项目升级到MVC2最简单的方法
- Ubuntu配置Open BlockChain
- C# virtual和abstract的
- wxWidgets一个界面与数据分离的简单例子
- C#Stimulator项目>;>;>;C/C++ DLL的生成和调用,Windows下的多线程
- Android应用开发基础篇(10)-----Menu(菜单)
- samba的安装和配置
- KDevelop使用笔记【中文】
- Android开发简易教程
- LoggerOne
- android自定义xmls文件属性
- 2-08. 用扑克牌计算24点(25) (ZJU_PAT 数学 枚举)
- GPU并行的基础知识
- 实验吧—密码学——WP之 杯酒人生
- 探索未知种族之osg类生物---呼吸分解之事件循环一
- 【文文殿下】【洛谷】分治NTT模板
- Idea maven项目不能新建package和class的解决
热门文章
- LuoguP2378 因式分解II 题解
- AT2287 [ARC067B] Walk and Teleport 题解
- python 安装模块报错 response.py";, line 302, in _error_catcher
- springboot 整合activemq
- JAVA删除某个文件夹(递归删除文件夹的所有文件)
- 【LeetCode】1404. 将二进制表示减到 1 的步骤数 Number of Steps to Reduce a Number in Binary Representation to One
- 【LeetCode】342. Power of Four 解题报告(Python)
- 【LeetCode】695. Max Area of Island 解题报告(Python & C++)
- 【LeetCode】894. All Possible Full Binary Trees 解题报告(Python & C++)
- 1188 最大公约数之和 V2