133 lines
26 KiB
Go
133 lines
26 KiB
Go
package main
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import (
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"fmt"
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"math/rand"
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"time"
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)
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const (
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maxLevel = 32 // 最大层数
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probability = 0.5 // 层数生成概率因子
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)
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// SkipNode 跳表节点结构
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type SkipNode struct {
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key int
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value interface{}
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forward []*SkipNode // 各层的前进指针
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}
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// NewSkipNode 创建新节点
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func NewSkipNode(key int, value interface{}, level int) *SkipNode {
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return &SkipNode{
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key: key,
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value: value,
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forward: make([]*SkipNode, level),
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}
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}
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// SkipList 跳表结构
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type SkipList struct {
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header *SkipNode // 头节点
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level int // 当前最大层数
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randSrc rand.Source // 随机数源
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}
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// NewSkipList 初始化跳表
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func NewSkipList() *SkipList {
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return &SkipList{
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header: NewSkipNode(0, nil, maxLevel),
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level: 1,
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randSrc: rand.NewSource(time.Now().UnixNano()),
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}
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}
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// randomLevel 生成随机层数 (抛硬币法)
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func (sl *SkipList) randomLevel() int {
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level := 1
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for ; level < maxLevel && sl.randSrc.Int63()&0xFFFF < int64(probability*0xFFFF); level++ {
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}
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return level
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}
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// Search 查找键对应的值
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func (sl *SkipList) Search(key int) (interface{}, bool) {
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current := sl.header
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// 从最高层开始查找
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for i := sl.level - 1; i >= 0; i-- {
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// 在当前层向右移动，直到找到大于等于key的节点
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for current.forward[i] != nil && current.forward[i].key < key {
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current = current.forward[i]
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}
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}
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// 移动到最底层(0层)的下一个节点
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current = current.forward[0]
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if current != nil && current.key == key {
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return current.value, true
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}
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return nil, false
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}
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// Insert 插入键值对
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func (sl *SkipList) Insert(key int, value interface{}) {
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update := make([]*SkipNode, maxLevel) // 各层需要更新的前驱节点
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current := sl.header
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// 1. 查找各层的前驱节点
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for i := sl.level - 1; i >= 0; i-- {
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for current.forward[i] != nil && current.forward[i].key < key {
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current = current.forward[i]
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}
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update[i] = current
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}
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// 2. 检查是否已存在相同key
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current = current.forward[0]
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if current != nil && current.key == key {
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current.value = value // 更新值
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return
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}
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// 3. 生成新节点的随机层数
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newLevel := sl.randomLevel()
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if newLevel > sl.level {
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// 补充高层的前驱节点为header
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for i := sl.level; i < newLevel; i++ {
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update[i] = sl.header
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}
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sl.level = newLevel
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}
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// 4. 创建新节点并插入各层
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newNode := NewSkipNode(key, value, newLevel)
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for i := 0; i < newLevel; i++ {
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newNode.forward[i] = update[i].forward[i]
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update[i].forward[i] = newNode
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}
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}
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// Delete 删除指定键的节点
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func (sl *SkipList) Delete(key int) bool {
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update := make([]*SkipNode, maxLevel)
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current := sl.header
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// 1. 查找各层的前驱节点
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for i := sl.level - 1; i >= 0; i-- {
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for current.forward[i] != nil && current.forward[i].key < key {
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current = current.forward[i]
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}
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update[i] = current
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}
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// 2. 定位到目标节点
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current = current.forward[0]
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if current == nil || current.key != key {
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return false // 未找到
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}
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// 3. 从各层链表中移除
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for i := 0; i < sl.level; i++ {
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if update[i].forward[i] != current {
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break // 上层已
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