Go language jump table (SkipList)

Go language jump table (SkipList)

The Skip table (skiplist) is a core data structure in redis/levelDB. I simply and rudely implemented it using Golang.

In my simple understanding, a common linked list converts a layer into multiple layers through Random_level () during insert,

The smaller the data, the larger the span. Search from top to bottom and use space for time.

Write down the test code:

 

package mainimport ("fmt"//"github.com/xclpkg/algorithm""math/rand")func main() {slt := NewSkipList()for i := 100; i > 0; i-- {slt.Insert(i)}slt.PrintSkipList()slt.Search(20)slt.Search(36)slt.Search(93)slt.Delete(55)slt.PrintSkipList()}const SKIPLIST_MAXLEVEL = 8 //32const SKIPLIST_P = 4type SkipList struct {Header []ListLevel  int}func NewSkipList() *SkipList {return &SkipList{Level: 1, Header: make([]List, SKIPLIST_MAXLEVEL)}}func (skipList *SkipList) Insert(key int) {update := make(map[int]*Node)for i := len(skipList.Header) - 1; i >= 0; i-- {if skipList.Header[i].Len() > 0 {for e := skipList.Header[i].Front(); e != nil; e = e.Next() {if e.Value.(int) >= key {update[i] = ebreak}}} //Heaer[lv].List} //Header Levellevel := skipList.Random_level()if level > skipList.Level {skipList.Level = level}for i := 0; i < level; i++ {if v, ok := update[i]; ok {skipList.Header[i].InsertBefore(key, v)} else {skipList.Header[i].PushBack(key)}}}func (skipList *SkipList) Search(key int) *Node {for i := len(skipList.Header) - 1; i >= 0; i-- {if skipList.Header[i].Len() > 0 {for e := skipList.Header[i].Front(); e != nil; e = e.Next() {switch {case e.Value.(int) == key:fmt.Println("Found level=", i, " key=", key)return ecase e.Value.(int) > key:break}} //end for} //end if} //end forreturn nil}func (skipList *SkipList) Delete(key int) {for i := len(skipList.Header) - 1; i >= 0; i-- {if skipList.Header[i].Len() > 0 {for e := skipList.Header[i].Front(); e != nil; e = e.Next() {switch {case e.Value.(int) == key:fmt.Println("Delete level=", i, " key=", key)skipList.Header[i].remove(e)case e.Value.(int) > key:break}} //end for} //end if} //end for}func (skipList *SkipList) PrintSkipList() {fmt.Println("\nSkipList-------------------------------------------")for i := SKIPLIST_MAXLEVEL - 1; i >= 0; i-- {fmt.Println("level:", i)if skipList.Header[i].Len() > 0 {for e := skipList.Header[i].Front(); e != nil; e = e.Next() {fmt.Printf("%d ", e.Value)} //end for} //end iffmt.Println("\n--------------------------------------------------------")} //end for}func (skipList *SkipList) Random_level() int {level := 1for (rand.Int31()&0xFFFF)%SKIPLIST_P == 0 {level += 1}if level < SKIPLIST_MAXLEVEL {return level} else {return SKIPLIST_MAXLEVEL}}//////////////////////////////////////////////////////type Node struct {next, prev *Nodelist       *ListValue interface{}}type List struct {root Nodelen  int}func (node *Node) Next() *Node {if p := node.next; node.list != nil && p != &node.list.root {return p}return nil}func (node *Node) Prev() *Node {if p := node.prev; node.list != nil && p != &node.list.root {return p}return nil}func (list *List) Init() *List {list.root.next = &list.rootlist.root.prev = &list.rootlist.len = 0return list}func New() *List {return new(List).Init()}func (list *List) lazyInit() {if list.root.next == nil {list.Init()}}func (list *List) Len() int {return list.len}func (list *List) remove(e *Node) *Node {e.prev.next = e.nexte.next.prev = e.preve.next = nile.prev = nile.list = nillist.len--return e}func (list *List) Remove(e *Node) interface{} {if e.list == list {list.remove(e)}return e.Value}func (list *List) Front() *Node {if list.len == 0 {return nil}return list.root.next}func (list *List) Back() *Node {if list.len == 0 {return nil}return list.root.prev}func (list *List) insert(e, at *Node) *Node {n := at.nextat.next = ee.prev = ate.next = nn.prev = ee.list = listlist.len++return e}func (list *List) insertValue(v interface{}, at *Node) *Node {return list.insert(&Node{Value: v}, at)}func (list *List) InsertBefore(v interface{}, mark *Node) *Node {if mark.list != list {return nil}return list.insertValue(v, mark.prev)}func (list *List) PushBack(v interface{}) *Node {list.lazyInit()return list.insertValue(v, list.root.prev)}

Effect:

SkipList-------------------------------------------level: 7--------------------------------------------------------level: 6--------------------------------------------------------level: 5--------------------------------------------------------level: 4--------------------------------------------------------level: 393--------------------------------------------------------level: 236 93--------------------------------------------------------level: 16 10 22 23 25 36 42 47 48 54 55 61 72 75 78 82 89 93--------------------------------------------------------level: 01 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 8384 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100--------------------------------------------------------Found level= 0  key= 20Found level= 2  key= 36Found level= 3  key= 93Delete level= 1  key= 55Delete level= 0  key= 55SkipList-------------------------------------------level: 7--------------------------------------------------------level: 6--------------------------------------------------------level: 5--------------------------------------------------------level: 4--------------------------------------------------------level: 393--------------------------------------------------------level: 236 93--------------------------------------------------------level: 16 10 22 23 25 36 42 47 48 54 61 72 75 78 82 89 93--------------------------------------------------------level: 01 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 8485 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100--------------------------------------------------------

Done.