摘要：
Given a linked list, determine if it has a cycle in it. Follow up:Can you solve it without using extra space? 题目要求判断链表是否有环形，题目不难，方法很巧，典型的双指针问题，一开始现实判断 阅读全文
摘要：
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 阅读全文