题目描述：
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 v and w as the ...
作者归档：在线疯狂
[LeetCode]Lowest Common Ancestor of a Binary Tree
[LeetCode]Lowest Common Ancestor of a Binary Search Tree
作者是
发布于
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LeetCode.
题目描述：
Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.
According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and ...
[LeetCode]Linked List Cycle II
作者是
发布于
在
LeetCode.
题目描述：
Given a linked list, return the node where the cycle begins. If there is no cycle, return null.
Follow up:
Can you solve it without using extra space?
题目大意：
给定一个链表，返回循环的起始节点。如果没有环，则返回空。
进一步思考：
你可以在不使用额外空间的条件下完成题目吗？
解题思路：
参考LeetCode Discuss（https://leetcode.com/discuss/16567/concise-solution-using-with-detailed-alogrithm-description）
1). 使用快慢指针法，若链表中有环，可以得到两指针的交点M 2). 记链表的头节点为H，环的起点为E ...
[LeetCode]Palindrome Linked List
作者是
发布于
在
LeetCode.
题目描述：
Given a singly linked list, determine if it is a palindrome.
Follow up:
Could you do it in O(n) time and O(1) space?
题目大意：
给定一个单链表，判断它是否是回文。
进一步思考：
你可以在O(n)时间复杂度和O(1)空间复杂度完成吗？
解题思路：
1). 使用快慢指针寻找链表中点
2). 将链表的后半部分就地逆置，然后比对前后两半的元素是否一致
3). 恢复原始链表的结构（可选）
Python代码：
# Definition for singly-linked ...
[LeetCode]Number of Digit One
作者是
发布于
在
LeetCode.
题目描述：
Given an integer n, count the total number of digit 1 appearing in all non-negative integers less than or equal to n.
For example:
Given n = 13,
Return 6, because digit 1 occurred in the following numbers: 1, ...