Leedcode10-linked-list-cycle-ii

判断是不是循环链表，如果是，返回它的第一个结点

首先判断，判断完之后，遍历循环链表，将它的指针域置为空，则循环到链表的第一个结点时，由于指针域为空，返回

#include<iostream>
#include<vector>
using namespace std;
/*
Given a linked list, return the node where the cycle begins. If there is no cycle, returnnull.
Follow up:
Can you solve it without using extra space?*/
struct ListNode {int val;ListNode *next;ListNode(int x) : val(x), next(NULL) {}
};
class Solution {
public:bool hasCycle(ListNode *head) {if (head == NULL)return false;ListNode* faster = head;ListNode* slower = head;while (faster->next->next != NULL && faster->next != NULL) {slower = slower->next;faster = faster->next->next;if (faster == slower)return true;}return false;}
};
//class Solution {  //没有通过所有测试用例
//public:
//  ListNode *detectCycle(ListNode *head) {
//      if (head == NULL)
//          return NULL;
//      ListNode* faster = head;
//      ListNode* slower = head;
//      while (faster->next->next != NULL && faster->next != NULL) {
//          slower = slower->next;
//          faster = faster->next->next;
//          if (faster == slower)   //当他两第一轮相同时，正好是最后一个结点
//              return slower;
//      }
//      return NULL;
//  }
//};
class Solution {
public:bool hasCycle(ListNode *head) {ListNode *fast = head;ListNode *slow = head;while (fast != NULL && fast->next != NULL) {fast = fast->next->next;slow = slow->next;if (fast == slow)return true;}return false;}ListNode *detectCycle(ListNode *head) {if (hasCycle(head)) {ListNode *temp = head;while (head->next) {temp = head->next;head->next = NULL;head = temp;}return head;}else {return NULL;}}
};

Leedcode10-linked-list-cycle-ii相关推荐

leetcode day5 -- Reorder List Linked List Cycle II
1. Reorder List Given a singly linked list L: L0→L1→-→Ln-1→Ln, reorder it to: L0→Ln→L1→Ln-1→L2→Ln ...
LeetCode141 Linked List Cycle. LeetCode142 Linked List Cycle II
链表相关题 141. Linked List Cycle Given a linked list, determine if it has a cycle in it. Follow up: Can ...
Leetcode 142. Linked List Cycle II
地址:Leetcode 142. linked list Cycle II 问题描述:检测链表是否存在环,是的话返回环入口,否则返回None. 这道题有两个思路,一个是经典的快慢指针的思路,另外一个是 ...
LeetCode 142. 环形链表 II(Linked List Cycle II)
142. 环形链表 II 142. Linked List Cycle II 题目描述给定一个链表,返回链表开始入环的第一个节点.如果链表无环,则返回 null. 为了表示给定链表中的环,我们使用整 ...
【To Do】LeetCode 142. Linked List Cycle II
LeetCode 142. Linked List Cycle II Solution1:我的答案这道题多次遇到,牢记此解法这道题要深思一下,快指针和慢指针的速度对比不同,会产生什么不同的结果? ...
Linked List Cycle II
Given a linked list, return the node where the cycle begins. If there is no cycle, return null. Foll ...
leetcode: Linked List Cycle II
http://oj.leetcode.com/problems/linked-list-cycle-ii/ Given a linked list, return the node where the ...
Leetcode 142 Linked List Cycle II
Given a linked list, return the node where the cycle begins. If there is no cycle, return null. Foll ...
【LeetCode】142 - Linked List Cycle II
Given a linked list, return the node where the cycle begins. If there is no cycle, return null. Foll ...
LeetCode Linked List Cycle II(floyd cycle)
问题:给出一个链表,可能存在环,要求输出环的起点位置思路:使用Floyd cycle algorithm 具体代码参考: https://github.com/wuli2496/OJ/tree/ma ...

Leedcode10-linked-list-cycle-ii

Leedcode10-linked-list-cycle-ii相关推荐

最新文章

热门文章