跳表 by golang

go/17_skiplist/skiplist.go

@@ -0,0 +1,177 @@
+package _7_skiplist
+
+import (
+	"fmt"
+	"math"
+	"math/rand"
+)
+
+const (
+	//最高层数
+	MAX_LEVEL = 16
+)
+
+//跳表节点结构体
+type skipListNode struct {
+	//跳表保存的值
+	v interface{}
+	//用于排序的分值
+	score int
+	//层高
+	level int
+	//每层前进指针
+	forwards []*skipListNode
+}
+
+//新建跳表节点
+func newSkipListNode(v interface{}, score, level int) *skipListNode {
+	return &skipListNode{v: v, score: score, forwards: make([]*skipListNode, level, level), level: level}
+}
+
+//跳表结构体
+type SkipList struct {
+	//跳表头结点
+	head *skipListNode
+	//跳表当前层数
+	level int
+	//跳表长度
+	length int
+}
+
+//实例化跳表对象
+func NewSkipList() *SkipList {
+	//头结点，便于操作
+	head := newSkipListNode(0, math.MinInt32, MAX_LEVEL)
+	return &SkipList{head, 1, 0}
+}
+
+//获取跳表长度
+func (sl *SkipList) Length() int {
+	return sl.length
+}
+
+//获取跳表层级
+func (sl *SkipList) Level() int {
+	return sl.level
+}
+
+//插入节点到跳表中
+func (sl *SkipList) Insert(v interface{}, score int) int {
+	if nil == v {
+		return 1
+	}
+
+	//查找插入位置
+	cur := sl.head
+	//记录每层的路径
+	update := [MAX_LEVEL]*skipListNode{}
+	i := MAX_LEVEL - 1
+	for ; i >= 0; i-- {
+		for nil != cur.forwards[i] {
+			if cur.forwards[i].v == v {
+				return 2
+			}
+			if cur.forwards[i].score > score {
+				update[i] = cur
+				break
+			}
+			cur = cur.forwards[i]
+		}
+		if nil == cur.forwards[i] {
+			update[i] = cur
+		}
+	}
+
+	//通过随机算法获取该节点层数
+	level := 1
+	for i := 1; i < MAX_LEVEL; i++ {
+		if rand.Int31()%7 == 1 {
+			level++
+		}
+	}
+
+	//创建一个新的跳表节点
+	newNode := newSkipListNode(v, score, level)
+
+	//原有节点连接
+	for i := 0; i <= level-1; i++ {
+		next := update[i].forwards[i]
+		update[i].forwards[i] = newNode
+		newNode.forwards[i] = next
+	}
+
+	//如果当前节点的层数大于之前跳表的层数
+	//更新当前跳表层数
+	if level > sl.level {
+		sl.level = level
+	}
+
+	//更新跳表长度
+	sl.length++
+
+	return 0
+}
+
+//查找
+func (sl *SkipList) Find(v interface{}, score int) *skipListNode {
+	if nil == v || sl.length == 0 {
+		return nil
+	}
+
+	cur := sl.head
+	for i := sl.level - 1; i >= 0; i-- {
+		for nil != cur.forwards[i] {
+			if cur.forwards[i].score == score && cur.forwards[i].v == v {
+				return cur.forwards[i]
+			} else if cur.forwards[i].score > score {
+				break
+			}
+			cur = cur.forwards[i]
+		}
+	}
+
+	return nil
+}
+
+//删除节点
+func (sl *SkipList) Delete(v interface{}, score int) int {
+	if nil == v {
+		return 1
+	}
+
+	//查找前驱节点
+	cur := sl.head
+	//记录前驱路径
+	update := [MAX_LEVEL]*skipListNode{}
+	for i := sl.level - 1; i >= 0; i-- {
+		update[i] = sl.head
+		for nil != cur.forwards[i] {
+			if cur.forwards[i].score == score && cur.forwards[i].v == v {
+				update[i] = cur
+				break
+			}
+			cur = cur.forwards[i]
+		}
+	}
+
+	cur = update[0].forwards[0]
+	for i := cur.level - 1; i >= 0; i-- {
+		if update[i] == sl.head && cur.forwards[i] == nil {
+			sl.level = i
+		}
+
+		if nil == update[i].forwards[i] {
+			update[i].forwards[i] = nil
+		} else {
+			update[i].forwards[i] = update[i].forwards[i].forwards[i]
+		}
+	}
+
+	sl.length--
+
+	return 0
+}
+
+func (sl *SkipList) String() string {
+	return fmt.Sprintf("level:%+v, length:%+v", sl.level, sl.length)
+}

go/17_skiplist/skiplist_test.go

@@ -0,0 +1,38 @@
+package _7_skiplist
+
+import "testing"
+
+func TestSkipList(t *testing.T) {
+	sl := NewSkipList()
+
+	sl.Insert("leo", 95)
+	t.Log(sl.head.forwards[0])
+	t.Log(sl.head.forwards[0].forwards[0])
+	t.Log(sl)
+	t.Log("-----------------------------")
+
+	sl.Insert("jack", 88)
+	t.Log(sl.head.forwards[0])
+	t.Log(sl.head.forwards[0].forwards[0])
+	t.Log(sl.head.forwards[0].forwards[0].forwards[0])
+	t.Log(sl)
+	t.Log("-----------------------------")
+
+	sl.Insert("lily", 100)
+	t.Log(sl.head.forwards[0])
+	t.Log(sl.head.forwards[0].forwards[0])
+	t.Log(sl.head.forwards[0].forwards[0].forwards[0])
+	t.Log(sl.head.forwards[0].forwards[0].forwards[0].forwards[0])
+	t.Log(sl)
+	t.Log("-----------------------------")
+
+	t.Log(sl.Find("jack", 88))
+	t.Log("-----------------------------")
+
+	sl.Delete("leo", 95)
+	t.Log(sl.head.forwards[0])
+	t.Log(sl.head.forwards[0].forwards[0])
+	t.Log(sl.head.forwards[0].forwards[0].forwards[0])
+	t.Log(sl)
+	t.Log("-----------------------------")
+}