Given a linked list, determine if it has a cycle in it.

Follow up:
Can you solve it without using extra space?

Solution: solve the problem with one and two steps

no cycle case: the faster pointer(two step) reaches the null first

cycle : slower == faster

Caution: check the null case

/**
* Definition for singly-linked list.
* class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
public boolean hasCycle(ListNode head) {
if(head == null) return false;
if(head.next == null) return false;
//with extra space
//a -> b ->c -> d -> a;
ListNode one = head;
ListNode two = head;
while(two.next != null && two.next.next !=null){
one = one.next;
two = two.next.next;
if(one==two) return true;
}
return false;
}
}

141. Linked List Cycle (amazon)的更多相关文章

  1. 141. Linked List Cycle&142. Linked List Cycle II(剑指Offer-链表中环的入口节点)

    题目: 141.Given a linked list, determine if it has a cycle in it. 142.Given a linked list, return the ...

  2. leetcode 141. Linked List Cycle 、 142. Linked List Cycle II

    判断链表有环,环的入口结点,环的长度 1.判断有环: 快慢指针,一个移动一次,一个移动两次 2.环的入口结点: 相遇的结点不一定是入口节点,所以y表示入口节点到相遇节点的距离 n是环的个数 w + n ...

  3. 141. Linked List Cycle(判断链表是否有环)

    141. Linked List Cycle Given a linked list, determine if it has a cycle in it. Follow up:Can you sol ...

  4. 【算法分析】如何理解快慢指针?判断linked list中是否有环、找到环的起始节点位置。以Leetcode 141. Linked List Cycle, 142. Linked List Cycle II 为例Python实现

    引入 快慢指针经常用于链表(linked list)中环(Cycle)相关的问题.LeetCode中对应题目分别是: 141. Linked List Cycle 判断linked list中是否有环 ...

  5. 141. Linked List Cycle【easy】

    141. Linked List Cycle[easy] Given a linked list, determine if it has a cycle in it. Follow up:Can y ...

  6. 141. Linked List Cycle - LeetCode

    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 ...

  7. [LeetCode] 141. Linked List Cycle 单链表中的环

    Given a linked list, determine if it has a cycle in it. To represent a cycle in the given linked lis ...

  8. 【LeetCode】141. Linked List Cycle (2 solutions)

    Linked List Cycle Given a linked list, determine if it has a cycle in it. Follow up:Can you solve it ...

  9. [LeetCode] 141. Linked List Cycle 链表中的环

    Given a linked list, determine if it has a cycle in it. Follow up:Can you solve it without using ext ...

随机推荐

  1. TreeMap读源码总结

    红黑树: 定义 A red–black tree is a kind of self-balancing binary search tree in computer science. Each no ...

  2. http 和 https 的区别

    参考:http://www.cnblogs.com/wqhwe/p/5407468.html HTTP:是互联网上应用最为广泛的一种网络协议,是一个客户端和服务器端请求和应答的标准(TCP),用于从W ...

  3. kafka删除主题数据和删除主题

    1.删除主题 在server.properties中增加设置,默认未开启 delete.topic.enable=true 删除主题命令 /bin/kafka-topics --delete --to ...

  4. 8 Operator overloading

    在类中,Groovy支持你使用标准的操作符.例如,如果你想使用a+b操作(a和b来自于Z类),那么你在Z类中,必须实现(implement)plus(Zname)方法.

  5. Juniper SRX550防火墙web页面CPU达到100%的故障解决办法

    Juniper SRX550防火墙web页面CPU达到100%的故障解决办法 利用telnet远程连接主机,对web页面注销重新登录即可,在配置中输入命令:run restart web-manage ...

  6. php 二维数组自定义排序

    eg1:只根据一个规则进行排序,比如我下面的数组是一组满减折扣的信息,我要按照满减的金额从小到大排序 代码: <?php $arr =[ ["amount"=> 60, ...

  7. java——arr == null || arr.length == 0

    这两者是不同的: arr == null; int[] arr = null; arr.length == 0; int[] arr =new int[0];

  8. call and apply

    apply()把参数打包成Array再传入: call()把参数按顺序传入. Math.max.apply(null, [3, 5, 4]); // 5 Math.max.call(null, 3, ...

  9. DexClassLoader和PathClassLoader

    Android的ClassLoader体系 在Android中可以跟java一样实现动态加载jar,但是Android使用Dalvik VM,不能直接加载java打包jar的byte code,需要通 ...

  10. Android Studio CMake 生成多个so

    生成多个so案例 这里stringFromJNI和stringFromJNI11分别是调用one-lib和two-lib两个so package com.test.ndkmoreso; import ...