#头条创作挑战赛#
在原始链表一个个查询的基础上增加索引跳过整个列表中的几个元素。如查找7从顶层开始1→7→13,发现13大于7则进入下一层直到原始链表中的7比原来从1到7减少多次查询。
如何判断这个数据插在哪里
从跳表的当前的最大层开始查找,在当前水平地逐个比较直到当前节点的下个节点大于等于目标节点,
for (int i = level - 1; i >= 0; i--) {
/* 找到第 i 层小于且最接近 num 的元素*/
while (curr.forward[i] != null && curr.forward[i].val < num) {
curr = curr.forward[i];
}
update[i] = curr;
}
然后移动到下一层查找,重复直到第一层。设新加入的节点为newNode,计算这个二节点插入的层数lv,
private int randomLevel() {
int lv = 1;
/* 随机生成 lv */
while (random.nextDouble() < P_FACTOR && lv < MAX_LEVEL) {
lv++;
}
return lv;
}
如果level小于lv,则同时更新level。用数组update保存每一层查找的最后一个结点,第i层最后的结点为update[i]。将newNode的后续结点指向update[i]的下个节点,同时更新update[i]的后续结点为newNode.
for (int i = 0; i < lv; i++) {
/* 对第 i 层的状态进行更新,将当前元素的 forward 指向新的节点 */
newNode.forward[i] = update[i].forward[i];
update[i].forward[i] = newNode;
}
和 b+树比哪个效率更高
B+树需要调整树结构,算法较复杂。增加和删除上需要维护索引。
跳表只需要处理链表。通过randomLevel获取lv,删除和更新时链表本身优势数据变动少,负载因子默认0.25,lv32.
跳表是Redis的有序集合zset的实现之一
class Skiplist {
static final int MAX_LEVEL = 32;
static final double P_FACTOR = 0.25;
private SkiplistNode head;
private int level;
private Random random;
public Skiplist() {
this.head = new SkiplistNode(-1, MAX_LEVEL);
this.level = 0;
this.random = new Random();
}
public boolean search(int target) {
SkiplistNode curr = this.head;
for (int i = level - 1; i >= 0; i--) {
/* 找到第 i 层小于且最接近 target 的元素*/
while (curr.forward[i] != null && curr.forward[i].val < target) {
curr = curr.forward[i];
}
}
curr = curr.forward[0];
/* 检测当前元素的值是否等于 target */
if (curr != null && curr.val == target) {
return true;
}
return false;
}
public void add(int num) {
SkiplistNode[] update = new SkiplistNode[MAX_LEVEL];
Arrays.fill(update, head);
SkiplistNode curr = this.head;
for (int i = level - 1; i >= 0; i--) {
/* 找到第 i 层小于且最接近 num 的元素*/
while (curr.forward[i] != null && curr.forward[i].val < num) {
curr = curr.forward[i];
}
update[i] = curr;
}
int lv = randomLevel();
level = Math.max(level, lv);
SkiplistNode newNode = new SkiplistNode(num, lv);
for (int i = 0; i < lv; i++) {
/* 对第 i 层的状态进行更新,将当前元素的 forward 指向新的节点 */
newNode.forward[i] = update[i].forward[i];
update[i].forward[i] = newNode;
}
}
public boolean erase(int num) {
SkiplistNode[] update = new SkiplistNode[MAX_LEVEL];
SkiplistNode curr = this.head;
for (int i = level - 1; i >= 0; i--) {
/* 找到第 i 层小于且最接近 num 的元素*/
while (curr.forward[i] != null && curr.forward[i].val < num) {
curr = curr.forward[i];
}
update[i] = curr;
}
curr = curr.forward[0];
/* 如果值不存在则返回 false */
if (curr == null || curr.val != num) {
return false;
}
for (int i = 0; i < level; i++) {
if (update[i].forward[i] != curr) {
break;
}
/* 对第 i 层的状态进行更新,将 forward 指向被删除节点的下一跳 */
update[i].forward[i] = curr.forward[i];
}
/* 更新当前的 level */
while (level > 1 && head.forward[level - 1] == null) {
level--;
}
return true;
}
private int randomLevel() {
int lv = 1;
/* 随机生成 lv */
while (random.nextDouble() < P_FACTOR && lv < MAX_LEVEL) {
lv++;
}
return lv;
}
}
class SkiplistNode {
int val;
SkiplistNode[] forward;
public SkiplistNode(int val, int maxLevel) {
this.val = val;
this.forward = new SkiplistNode[maxLevel];
}
}
「链接」William Pugh 「Skip Lists: A Probabilistic Alternative to Balanced Trees」
力扣leetcode 设计跳表
数据结构——跳表skip list_Overcautious的博客-CSDN博客_跳表数据库randomlevel 什么用
页面更新:2024-05-28
本站资料均由网友自行发布提供,仅用于学习交流。如有版权问题,请与我联系,QQ:4156828
© CopyRight 2020-2024 All Rights Reserved. Powered By 71396.com 闽ICP备11008920号-4
闽公网安备35020302034903号