Question 141. Linked List Cycle Solution 题目大意:给一个链表,判断是否存在循环,最好不要使用额外空间 思路:定义一个假节点fakeNext,遍历这个链表,判断该节点的next与假节点是否相等,如果不等为该节点的next赋值成fakeNext Java实现: public boolean hasCycle(ListNode head) { // check if head null if (head == null) return false; ListN…

Given a linked list, determine if it has a cycle in it. Follow up:Can you solve it without using extra space? 题目大意:给定一个链表,判断是否有环? 解题思路: 解法一:快慢指针,如果有环,那么快慢指针总会相遇,有环:否则快的遍历完整个链表,无环. 解法二:HashSet保存节点,如果下一个节点在set中出现过,那么有环,否则直到遍历完整个链表,无环. Talk is cheap>>…

题目: 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? 题解: 这个连同I都是很经典的题啦,刷CC150时候就折磨了半天. 其实就推几个递推公式就好..首先看图(图引用自CC150): 从链表起始处到环入口长度为:a,从环入口到Faster和Sl…

题目: Given a linked list, determine if it has a cycle in it. Follow up: Can you solve it without using extra space? 题解: 这道题连带着II是很经典的,在看CC150时候,纠结这个问题纠结了很久.在读了很多网上资料还有书的讲解以及和别人讨论之后,对这个专题终于明白了. 这一问只需要判断链表是否有环. 当链表没有环时是很好判断的,让一个指针一直往后走,遇见null了自然就没有环. 而如…

Given a linked list, determine if it has a cycle in it. Follow up:Can you solve it without using extra space? 思路:维护两个指针,一快一慢,判断两个指针能否相遇. class Solution { public: bool hasCycle(ListNode *head) { if (head == NULL) return false; ListNode *slow = head; i…

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? 这个求单链表中的环的起始点是之前那个判断单链表中是否有环的延伸,可参见我之前的一篇文章 (http://www.cnblogs.com/grandyang/p/4137187.html). 还是要设…

Given a linked list, determine if it has a cycle in it. Follow up: Can you solve it without using extra space? 这道题是快慢指针的经典应用.只需要设两个指针,一个每次走一步的慢指针和一个每次走两步的快指针,如果链表里有环的话,两个指针最终肯定会相遇.实在是太巧妙了,要是我肯定想不出来.代码如下: C++ 解法: class Solution { public: bool hasCycle…

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? 解题思路,本题和上题十分类似,但是需要观察出一个规律,参考LeetCode:Linked List Cycle II JAVA实现如下: public ListNode detectCycle(Li…

LeetCode解题报告:Linked List Cycle && Linked List Cycle II 1题目 Linked List Cycle Given a linked list, determine if it has a cycle in it. Follow up: Can you solve it without using extra space? Linked List Cycle II Given a linked list, return the node w…

Problem: Given a linked list, determine if it has a cycle in it. Follow up:Can you solve it without using extra space? https://oj.leetcode.com/problems/linked-list-cycle/ Problem II: Given a linked list, return the node where the cycle begins. If the…