Coding for Dreams

Sort a linked list in O(n log n) time using constant space complexity.思路分析：这题要求在O(n log n) 和常量空间对单链表排序，O(n log n) 的排序算法有快速排序，归并排序和堆排序，对于快速排序，其最坏情况下的时间复杂读是O（n），所以不符合要求。我们可以用归并排序解决这题。用归并排序的好处是平均时间和最坏时间都

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.思路分析：这题是 LeetCode Sort List需要使用的merge两个有序链表使得结果仍然有序这个子过程，详细

Given a linked list, determine if it has a cycle in it.Follow up:Can you solve it without using extra space?思路分析：这题很简单，直接用快慢指针法就可以解决，快指针速度是慢指针速度的2倍，如果有环，它们一定会相遇。AC Code/** * Definition for singly-lin

Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is.You

Reverse a linked list from position m to n. Do it in-place and in one-pass.For example:Given 1->2->3->4->5->NULL, m = 2 and n = 4,return 1->4->3->2->5->NULL.Note:Given m, n satisfy the following condi

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?思路分析：这题比较容易想到的解法是先检查是否有环，然后检查每个node是否在环内，但是是O（N^2）的解

Write a program to find the node at which the intersection of two singly linked lists begins.For example, the following two linked lists:A: a1 → a2 ↘ c

A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.Return a deep copy of the list.思路分析：这题要求拷贝链表，包括内容，next指针和random指针。容易想