{ "data": { "question": { "questionId": "100179", "questionFrontendId": "面试题 04.08", "categoryTitle": "LCCI", "boundTopicId": 46238, "title": "First Common Ancestor LCCI", "titleSlug": "first-common-ancestor-lcci", "content": "

Design an algorithm and write code to find the first common ancestor of two nodes in a binary tree. Avoid storing additional nodes in a data structure. NOTE: This is not necessarily a binary search tree.

\r\n\r\n

For example, Given the following tree: root = [3,5,1,6,2,0,8,null,null,7,4]

\r\n\r\n
\r\n    3\r\n   / \\\r\n  5   1\r\n / \\ / \\\r\n6  2 0  8\r\n  / \\\r\n 7   4\r\n
\r\n\r\n

Example 1:

\r\n\r\n
\r\nInput: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1\r\nInput: 3\r\nExplanation: The first common ancestor of node 5 and node 1 is node 3.
\r\n\r\n

Example 2:

\r\n\r\n
\r\nInput: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4\r\nOutput: 5\r\nExplanation: The first common ancestor of node 5 and node 4 is node 5.
\r\n\r\n

Notes:

\r\n\r\n\r\n", "translatedTitle": "首个共同祖先", "translatedContent": "

设计并实现一个算法，找出二叉树中某两个节点的第一个共同祖先。不得将其他的节点存储在另外的数据结构中。注意：这不一定是二叉搜索树。

\n\n

例如，给定如下二叉树: root = [3,5,1,6,2,0,8,null,null,7,4]

\n\n
    3\n   / \\\n  5   1\n / \\ / \\\n6  2 0  8\n  / \\\n 7   4\n
\n\n

示例 1:

\n\n
输入: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1\n输出: 3\n解释: 节点 5 和节点 1 的最近公共祖先是节点 3。
\n\n

示例 2:

\n\n
输入: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4\n输出: 5\n解释: 节点 5 和节点 4 的最近公共祖先是节点 5。因为根据定义最近公共祖先节点可以为节点本身。
\n\n

说明:

\n\n
所有节点的值都是唯一的。\np、q 为不同节点且均存在于给定的二叉树中。
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}\n * }\n */\nclass Solution {\n public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {\n\n }\n}", "__typename": "CodeSnippetNode" }, { "lang": "Python", "langSlug": "python", "code": "# Definition for a binary tree node.\n# class TreeNode(object):\n# def __init__(self, x):\n# self.val = x\n# self.left = None\n# self.right = None\n\nclass Solution(object):\n def lowestCommonAncestor(self, root, p, q):\n \"\"\"\n :type root: TreeNode\n :type p: TreeNode\n :type q: TreeNode\n :rtype: TreeNode\n \"\"\"", "__typename": "CodeSnippetNode" }, { "lang": "Python3", "langSlug": "python3", "code": "# Definition for a binary tree node.\n# class TreeNode:\n# def __init__(self, x):\n# self.val = x\n# self.left = None\n# self.right = None\n\nclass Solution:\n def lowestCommonAncestor(self, root: TreeNode, p: TreeNode, q: TreeNode) -> TreeNode:", "__typename": "CodeSnippetNode" }, { "lang": "C", "langSlug": "c", "code": "/**\n * Definition for a binary tree node.\n * struct TreeNode {\n * int val;\n * struct TreeNode *left;\n * struct TreeNode *right;\n * };\n */\n\n\nstruct TreeNode* lowestCommonAncestor(struct TreeNode* root, struct TreeNode* p, struct TreeNode* q){\n\n}\n", "__typename": "CodeSnippetNode" }, { "lang": "C#", "langSlug": "csharp", "code": "/**\n * Definition for a binary tree node.\n * public class TreeNode {\n * public int val;\n * public TreeNode left;\n * public TreeNode right;\n * public TreeNode(int x) { val = x; 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