LeetCode 1650. Lowest Common Ancestor of a Binary Tree III - 二叉树（Binary Tree）系列题3

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已于 2022-02-12 22:48:39 修改 · 437 阅读

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于 2022-02-12 22:47:33 首次发布

本篇博客主要介绍了LeetCode 1650题目的解决方法，即在二叉树中找到两个给定节点的最低公共祖先（LCA）。题目中每个节点包含指向父节点的引用。通过分析节点路径，可以发现问题与链表相交类似。提出了两种解决方案：一是使用集合记录一个节点的父节点路径，检查另一个节点的父节点是否在集合中；二是利用双指针技巧，沿着两个节点的父节点路径同步移动，找到公共祖先节点。

Given two nodes of a binary tree p and q, return their lowest common ancestor (LCA).

Each node will have a reference to its parent node. The definition for Node is below:

class Node {
    public int val;
    public Node left;
    public Node right;
    public Node parent;
}

According to the definition of LCA on Wikipedia: "The lowest common ancestor of two nodes p and q in a tree T is the lowest node that has both p and q as descendants (where we allow a node to be a descendant of itself)."

Example 1: