Given a singly linked list, return a random node's value from the linked list. Each node must have the same probability of being chosen. Follow up: What if the linked list is extremely large and its length is unknown to you? Could you solve this effi…

Given a singly linked list, return a random node's value from the linked list. Each node must have the same probability of being chosen. Follow up: What if the linked list is extremely large and its length is unknown to you? Could you solve this effi…

给定一个单链表,随机选择链表的一个节点,并返回相应的节点值.保证每个节点被选的概率一样.进阶:如果链表十分大且长度未知,如何解决这个问题?你能否使用常数级空间复杂度实现?示例:// 初始化一个单链表 [1,2,3].ListNode head = new ListNode(1);head.next = new ListNode(2);head.next.next = new ListNode(3);Solution solution = new Solution(head);// getRand…

这题参照http://blog.jobbole.com/42550/ 用的蓄水池算法,即更改ans的概率为1/(当前length) /** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */ public class Solution { private ListNode head; /**…

382. 链表随机节点 给定一个单链表,随机选择链表的一个节点,并返回相应的节点值.保证每个节点被选的概率一样. 进阶: 如果链表十分大且长度未知,如何解决这个问题?你能否使用常数级空间复杂度实现? 示例: // 初始化一个单链表 [1,2,3]. ListNode head = new ListNode(1); head.next = new ListNode(2); head.next.next = new ListNode(3); Solution solution = new Solut…

Given a singly linked list, return a random node's value from the linked list. Each node must have the same probability of being chosen. Follow up:What if the linked list is extremely large and its length is unknown to you? Could you solve this effic…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 数组保存再随机选择 蓄水池抽样 日期 题目地址:https://leetcode.com/problems/linked-list-random-node/description/ 题目描述 Given a singly linked list, return a random node's value from the linked list. E…

Given a singly linked list, return a random node's value from the linked list. Each node must have the same probability of being chosen. Follow up: What if the linked list is extremely large and its length is unknown to you? Could you solve this effi…

Given a singly linked list, return a random node's value from the linked list. Each node must have the same probability of being chosen. Follow up:What if the linked list is extremely large and its length is unknown to you? Could you solve this effic…

本题可以用reservoir sampling来解决不明list长度的情况下平均概率选择元素的问题. 假设在[x_1,...,x_n]只选一个元素,要求每个元素被选中的概率都是1/n,但是n未知. 其中 random.randint(0, cnt) == 0: 的概率是1/(cnt+1).reservoir sampling的证明可以使用归纳法(induction). class Solution(object): def __init__(self, head): """…

Given a singly linked list, return a random node's value from the linked list. Each node must have the same probability of being chosen. Follow up:What if the linked list is extremely large and its length is unknown to you? Could you solve this effic…

Given a singly linked list, return a random node's value from the linked list. Each node must have the same probability of being chosen. Follow up:What if the linked list is extremely large and its length is unknown to you? Could you solve this effic…

题目链接:https://leetcode-cn.com/problems/shan-chu-lian-biao-de-jie-dian-lcof/ 给定单向链表的头指针和一个要删除的节点的值,定义一个函数删除该节点. 返回删除后的链表的头节点. 注意:此题对比原题有改动 示例 1: 输入: head = [4,5,1,9], val = 5输出: [4,1,9]解释: 给定你链表中值为 5 的第二个节点,那么在调用了你的函数之后,该链表应变为 4 -> 1 -> 9.示例 2: 输入: he…

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…

1. 问题 给定一个单链表,随机返回一个结点,要求每个结点被选中的概率相等. 2. 思路 在一个给定长度的数组中等概率抽取一个数,可以简单用随机函数random.randint(0, n-1)得到索引来抽取. 本题是给定了链表,当然也好做,可以事先遍历一次求长度,每次要取的时候随机求索引,然后遍历一次. 时间复杂度O(n),空间复杂度O(1) 或者事先把数据放到数组中,每次要取的时候随机求索引,然后直接取到对应的数. 时间复杂度O(1),空间复杂度O(n) (延伸一下)如果对于长度未知,会不断增…

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? Hide Tags Linked List Two Pointers        开始犯二了一点,使用了node 的val 作为判断,其实是根据内存判断.找出链表环的起始位置,这个画一下慢慢找下规律…

Given a linked list, determine if it has a cycle in it. Follow up:Can you solve it without using extra space? 判断链表中是否有环,不能用额外的空间,可以使用快慢指针,慢指针一次走一步,快指针一次走两步,若是有环则快慢指针会相遇,若是fast->next==NULL则没有环. 值得注意的是:在链表的题中,快慢指针的使用频率还是很高,值得注意. /** * Definition for si…

题意:给一个单链表,判断其是否出现环! 思路:搞两个指针,每次,一个走两步,另一个走一步.若有环,他们会相遇,若无环,走两步的指针必定会先遇到NULL. /** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class Solution { public: bool has…

Given an array of integers with possible duplicates, randomly output the index of a given target number. You can assume that the given target number must exist in the array. Note: The array size can be very large. Solution that uses too much extra sp…

原题链接:[382. 链表随机节点]:https://leetcode-cn.com/problems/linked-list-random-node/ 题目描述: 给定一个单链表,随机选择链表的一个节点,并返回相应的节点值.保证每个节点被选的概率一样. 进阶: 如果链表十分大且长度未知,如何解决这个问题?你能否使用常数级空间复杂度实现? 示例: // 初始化一个单链表 [1,2,3]. ListNode head = new ListNode(1); head.next = new ListN…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 每次遍历索引 字典保存索引 蓄水池抽样 日期 题目地址:https://leetcode.com/problems/random-pick-index/description/ 题目描述 Given an array of integers with possible duplicates, randomly output the index of…

2.3 Implement an algorithm to delete a node in the middle of a singly linked list, given only access to that node.EXAMPLEInput: the node c from the linked list a->b->c->d->eResult: nothing is returned, but the new linked list looks like a- >…

作者: 负雪明烛 id: fuxuemingzhu 个人公众号:负雪明烛 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 日期 题目地址:https://leetcode-cn.com/problems/copy-list-with-random-pointer/ 题目描述 给你一个长度为 n 的链表,每个节点包含一个额外增加的随机指针 random ,该指针可以指向链表中的任何节点或空节点. 构造这个链表的 深拷贝. 深拷贝应该正好由 n 个 全…

一天一道LeetCode 本系列文章已全部上传至我的github,地址:ZeeCoder's Github 欢迎大家关注我的新浪微博,我的新浪微博 欢迎转载,转载请注明出处 (一)题目 Write a function to delete a node (except the tail) in a singly linked list, given only access to that node. Supposed the linked list is 1 -> 2 -> 3 -> 4…

题目: Given a linked list, determine if it has a cycle in it. To represent a cycle in the given linked list, we use an integer pos which represents the position (0-indexed) in the linked list where tail connects to. If pos is -1, then there is no cycle…

​ 请判断一个链表是否为回文链表. Given a singly linked list, determine if it is a palindrome. 示例 1: 输入: 1->2 输出: false 示例 2: 输入: 1->2->2->1 输出: true 进阶: 你能否用 O(n) 时间复杂度和 O(1) 空间复杂度解决此题? Follow up: Could you do it in O(n) time and O(1) space? 解题思路: 首先是寻找链表中间节…

题目来源于 LeetCode 第 23 号问题:合并 K 个排序链表. 该题在 LeetCode 官网上有关于链表的问题中标注为最难的一道题目:难度为 Hard ,通过率在链表 Hard 级别目前最低. 题目描述 合并 k 个排序链表,返回合并后的排序链表.请分析和描述算法的复杂度. 示例: 输入:[  1->4->5,  1->3->4,  2->6]输出: 1->1->2->3->4->4->5->6 输入 图一 输出 图二 题目…

Linked List & List Node All In One 链表 & 节点 链表类型 单链表 双链表 环形链表 / 循环链表 Singly Linked List (Uni-directional) Doubly Linked List (Bi-directional) Circular Linked List js 实现 Linked List "use strict"; /** * * @author xgqfrms * @license MIT * @c…

2.6 Given a circular linked list, implement an algorithm which returns the node at the beginning of the loop.DEFINITIONCircular linked list: A (corrupt) linked list in which a node's next pointer points to an earlier node, so as to make a loop in the…

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 ↘ c1 → c2 → c3 ↗ B: b1 → b2 → b3 求两个链表开始重合的地方,也就是交叉的地方.. 思路:两个链表从交叉的位置开始,后面的长度是相同的,前面的长度可能相等也可能不同.当前…