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skiplist.go
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skiplist.go
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package skiplist
import (
"fmt"
"math/rand"
)
const maxLevel = 32
const prob = 0.35
// SkipValue 跳跃表节点的Value值
type SkipValue struct {
Score int64
Value interface{}
}
//Compare Const
const (
Big = -1
Small = 1
Equal = 0
)
// Compare 比较函数,这样的比较排序是从大到小
func (v *SkipValue) Compare(value *SkipValue) int {
if v.Score > value.Score {
return Big
} else if v.Score == value.Score {
return Equal
}
return Small
}
// skipListNode 跳跃表节点
type skipListNode struct {
next []*skipListNode
prev *skipListNode
Value *SkipValue
}
// SkipList 跳跃表
type SkipList struct {
header, tail *skipListNode
findcount int
count int
level int
}
// Iterator 跳跃表迭代器
type Iterator struct {
list *SkipList
node *skipListNode
}
// First 获取第一个节点Value值
func (sli *Iterator) First() *SkipValue {
if sli.list.header.next[0] == nil {
return nil
}
sli.node = sli.list.header.next[0]
return sli.node.Value
}
// Last 获取最后一个节点Value值
func (sli *Iterator) Last() *SkipValue {
if sli.list.tail == nil {
return nil
}
sli.node = sli.list.tail
return sli.node.Value
}
// Prev 获取迭代器的上一个节点
func (sli *Iterator) Prev() *Iterator {
sli.node = sli.node.Prev()
return sli
}
// Next 获取迭代器的下一个节点
func (sli *Iterator) Next() *Iterator {
sli.node = sli.node.Next()
return sli
}
// Value 获取迭代器当前的Value
func (sli *Iterator) Value() *SkipValue {
return sli.node.Value
}
// Prev 获取上一个节点
func (node *skipListNode) Prev() *skipListNode {
if node == nil || node.prev == nil {
return nil
}
return node.prev
}
// Next 获取下一个节点
func (node *skipListNode) Next() *skipListNode {
if node == nil || node.next[0] == nil {
return nil
}
return node.next[0]
}
// Seek 迭代器在跳跃表中查找某个位置在传参后面或者与传参相等的SkipValue
func (sli *Iterator) Seek(value *SkipValue) *SkipValue {
x := sli.list.find(value)
if x.next[0] == nil {
return nil
}
sli.node = x.next[0]
return sli.node.Value
}
func newskipListNode(level int, value *SkipValue) *skipListNode {
node := &skipListNode{}
node.next = make([]*skipListNode, level)
node.Value = value
return node
}
//NewSkipList 构建一个跳跃表
func NewSkipList(min *SkipValue) *SkipList {
sl := &SkipList{}
sl.level = 1
sl.header = newskipListNode(maxLevel, min)
return sl
}
func randomLevel() int {
level := 1
t := prob * 0xFFFF
// #nosec
for rand.Int()&0xFFFF < int(t) {
level++
if level == maxLevel {
break
}
}
return level
}
// GetIterator 获取迭代器
func (sl *SkipList) GetIterator() *Iterator {
it := &Iterator{}
it.list = sl
it.First()
return it
}
// Len 返回节点数
func (sl *SkipList) Len() int {
return sl.count
}
// Level 返回跳跃表的层级
func (sl *SkipList) Level() int {
return sl.level
}
func (sl *SkipList) find(value *SkipValue) *skipListNode {
x := sl.header
for i := sl.level - 1; i >= 0; i-- {
for x.next[i] != nil && x.next[i].Value.Compare(value) < 0 {
sl.findcount++
x = x.next[i]
}
}
return x
}
// FindCount 返回查询次数
func (sl *SkipList) FindCount() int {
return sl.findcount
}
// Find 查找某个跳跃表中的SkipValue
func (sl *SkipList) Find(value *SkipValue) *SkipValue {
x := sl.find(value)
if x.next[0] != nil && x.next[0].Value.Compare(value) == 0 {
return x.next[0].Value
}
return nil
}
// FindGreaterOrEqual 在跳跃表中查找某个位置在传参后面或者与传参相等的SkipValue
func (sl *SkipList) FindGreaterOrEqual(value *SkipValue) *SkipValue {
x := sl.find(value)
if x.next[0] != nil {
return x.next[0].Value
}
return nil
}
// Insert 插入节点
func (sl *SkipList) Insert(value *SkipValue) int {
var update [maxLevel]*skipListNode
x := sl.header
for i := sl.level - 1; i >= 0; i-- {
for x.next[i] != nil && x.next[i].Value.Compare(value) <= 0 {
x = x.next[i]
}
update[i] = x
}
//if x.next[0] != nil && x.next[0].Value.Compare(value) == 0 { //update
// x.next[0].Value = value
// return 0
//}
level := randomLevel()
if level > sl.level {
for i := sl.level; i < level; i++ {
update[i] = sl.header
}
sl.level = level
}
x = newskipListNode(level, value)
for i := 0; i < level; i++ {
x.next[i] = update[i].next[i]
update[i].next[i] = x
}
//形成一个双向链表
if update[0] != sl.header {
x.prev = update[0]
}
if x.next[0] != nil {
x.next[0].prev = x
} else {
sl.tail = x
}
sl.count++
return 1
}
// Delete 删除节点
func (sl *SkipList) Delete(value *SkipValue) int {
if value == nil {
return 0
}
var update [maxLevel]*skipListNode
x := sl.header
for i := sl.level - 1; i >= 0; i-- {
for x.next[i] != nil && x.next[i].Value.Compare(value) < 0 {
x = x.next[i]
}
update[i] = x
}
if x.next[0] == nil || x.next[0].Value.Compare(value) != 0 { //not find
return 0
}
x = x.next[0]
for i := 0; i < sl.level; i++ {
if update[i].next[i] == x {
update[i].next[i] = x.next[i]
}
}
if x.next[0] != nil {
x.next[0].prev = x.prev
} else {
sl.tail = x.prev
}
for sl.level > 1 && sl.header.next[sl.level-1] == nil {
sl.level--
}
sl.count--
return 1
}
// Print 测试用的输出函数
func (sl *SkipList) Print() {
if sl.count > 0 {
r := sl.header
for i := sl.level - 1; i >= 0; i-- {
e := r.next[i]
//fmt.Print(i)
for e != nil {
fmt.Print(e.Value.Score)
fmt.Print(" ")
fmt.Print(e.Value)
fmt.Println("")
e = e.next[i]
}
fmt.Println()
}
} else {
fmt.Println("空")
}
}
//Walk 遍历整个结构中SkipValue的Value,如果cb 返回false 那么停止遍历
func (sl *SkipList) Walk(cb func(value interface{}) bool) {
for e := sl.header.Next(); e != nil; e = e.Next() {
if cb == nil {
return
}
if !cb(e.Value.Value) {
return
}
}
}
//WalkS 遍历整个结构中的SkipValue,如果cb 返回false 那么停止遍历
func (sl *SkipList) WalkS(cb func(value interface{}) bool) {
for e := sl.header.Next(); e != nil; e = e.Next() {
if cb == nil {
return
}
if !cb(e.Value) {
return
}
}
}