1650-lowest-common-ancestor-of-a-binary-tree-iii.adoc

1650. Lowest Common Ancestor of a Binary Tree III

{leetcode}/problems/lowest-common-ancestor-of-a-binary-tree-iii/[LeetCode - 1650. Lowest Common Ancestor of a Binary Tree III ^]

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:

**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.

Example 3:

**Input:** root = [1,2], p = 1, q = 2
**Output:** 1

Constraints:

• The number of nodes in the tree is in the range [2, 105].

• -109 ⇐ Node.val ⇐ 109

• All Node.val are unique.

• p != q

• p and q exist in the tree.

思路分析

这道题披着树的外衣，里面确实一个链接相交的芯。

一刷

link:{sourcedir}/_1650_LowestCommonAncestorOfABinaryTreeIII.java[role=include]

参考资料