178 lines
3.2 KiB
Go
178 lines
3.2 KiB
Go
package _7_skiplist
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import (
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"fmt"
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"math"
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"math/rand"
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)
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const (
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//最高层数
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MAX_LEVEL = 16
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)
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//跳表节点结构体
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type skipListNode struct {
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//跳表保存的值
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v interface{}
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//用于排序的分值
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score int
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//层高
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level int
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//每层前进指针
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forwards []*skipListNode
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}
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//新建跳表节点
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func newSkipListNode(v interface{}, score, level int) *skipListNode {
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return &skipListNode{v: v, score: score, forwards: make([]*skipListNode, level, level), level: level}
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}
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//跳表结构体
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type SkipList struct {
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//跳表头结点
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head *skipListNode
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//跳表当前层数
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level int
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//跳表长度
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length int
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}
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//实例化跳表对象
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func NewSkipList() *SkipList {
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//头结点，便于操作
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head := newSkipListNode(0, math.MinInt32, MAX_LEVEL)
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return &SkipList{head, 1, 0}
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}
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//获取跳表长度
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func (sl *SkipList) Length() int {
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return sl.length
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}
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//获取跳表层级
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func (sl *SkipList) Level() int {
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return sl.level
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}
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//插入节点到跳表中
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func (sl *SkipList) Insert(v interface{}, score int) int {
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if nil == v {
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return 1
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}
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//查找插入位置
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cur := sl.head
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//记录每层的路径
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update := [MAX_LEVEL]*skipListNode{}
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i := MAX_LEVEL - 1
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for ; i >= 0; i-- {
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for nil != cur.forwards[i] {
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if cur.forwards[i].v == v {
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return 2
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}
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if cur.forwards[i].score > score {
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update[i] = cur
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break
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}
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cur = cur.forwards[i]
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}
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if nil == cur.forwards[i] {
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update[i] = cur
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}
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}
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//通过随机算法获取该节点层数
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level := 1
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for i := 1; i < MAX_LEVEL; i++ {
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if rand.Int31()%7 == 1 {
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level++
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}
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}
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//创建一个新的跳表节点
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newNode := newSkipListNode(v, score, level)
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//原有节点连接
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for i := 0; i <= level-1; i++ {
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next := update[i].forwards[i]
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update[i].forwards[i] = newNode
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newNode.forwards[i] = next
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}
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//如果当前节点的层数大于之前跳表的层数
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//更新当前跳表层数
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if level > sl.level {
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sl.level = level
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}
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//更新跳表长度
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sl.length++
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return 0
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}
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//查找
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func (sl *SkipList) Find(v interface{}, score int) *skipListNode {
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if nil == v || sl.length == 0 {
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return nil
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}
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cur := sl.head
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for i := sl.level - 1; i >= 0; i-- {
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for nil != cur.forwards[i] {
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if cur.forwards[i].score == score && cur.forwards[i].v == v {
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return cur.forwards[i]
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} else if cur.forwards[i].score > score {
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break
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}
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cur = cur.forwards[i]
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}
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}
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return nil
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}
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//删除节点
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func (sl *SkipList) Delete(v interface{}, score int) int {
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if nil == v {
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return 1
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}
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//查找前驱节点
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cur := sl.head
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//记录前驱路径
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update := [MAX_LEVEL]*skipListNode{}
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for i := sl.level - 1; i >= 0; i-- {
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update[i] = sl.head
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for nil != cur.forwards[i] {
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if cur.forwards[i].score == score && cur.forwards[i].v == v {
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update[i] = cur
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break
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}
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cur = cur.forwards[i]
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}
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}
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cur = update[0].forwards[0]
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for i := cur.level - 1; i >= 0; i-- {
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if update[i] == sl.head && cur.forwards[i] == nil {
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sl.level = i
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}
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if nil == update[i].forwards[i] {
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update[i].forwards[i] = nil
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} else {
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update[i].forwards[i] = update[i].forwards[i].forwards[i]
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}
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}
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sl.length--
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return 0
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}
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func (sl *SkipList) String() string {
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return fmt.Sprintf("level:%+v, length:%+v", sl.level, sl.length)
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}
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