使用Go语言实现LRU缓存的代码详解

package main

import "fmt"

// 双向链表的节点
type Node struct {
	key, value int
	prev, next *Node
}

// LRUCache 缓存结构
type LRUCache struct {
	capacity   int
	cache      map[int]*Node // 哈希表，快速定位节点
	head, tail *Node         // 虚拟头尾节点
}

    head <--> tail

// 构造函数
func Constructor(capacity int) LRUCache {
	cache := LRUCache{
		capacity: capacity,
		cache:    make(map[int]*Node),
		head:     &Node{},
		tail:     &Node{},
	}
	cache.head.next = cache.tail
	cache.tail.prev = cache.head
	return cache
}

// 获取缓存中的值
func (this *LRUCache) Get(key int) int {
	if node, found := this.cache[key]; found {
		this.moveToHead(node) // 访问后移至头部
		return node.value
	}
	return -1 // 如果不存在，返回 -1
}

head <--> B <--> A <--> tail

// 更新或插入值
func (this *LRUCache) Put(key int, value int) {
	if node, found := this.cache[key]; found {
		node.value = value
		this.moveToHead(node) // 已存在的节点移至头部
	} else {
		// 创建新节点并加入头部
		newNode := &Node{key: key, value: value}
		this.cache[key] = newNode
		this.addNode(newNode)

		// 超出容量时，删除尾节点
		if len(this.cache) > this.capacity {
			tail := this.popTail()
			delete(this.cache, tail.key)
		}
	}
}

    head <--> C <--> B <--> tail

// 添加节点至头部
func (this *LRUCache) addNode(node *Node) {
	node.prev = this.head
	node.next = this.head.next
	this.head.next.prev = node
	this.head.next = node
}

// 删除节点
func (this *LRUCache) removeNode(node *Node) {
	prev := node.prev
	next := node.next
	prev.next = next
	next.prev = prev
}

// 移动节点到头部
func (this *LRUCache) moveToHead(node *Node) {
	this.removeNode(node)
	this.addNode(node)
}

// 弹出尾部节点
func (this *LRUCache) popTail() *Node {
	tail := this.tail.prev
	this.removeNode(tail)
	return tail
}

    head <--> node <--> A <--> B <--> tail

import "testing"

func TestLRUCache(t *testing.T) {
	cache := Constructor(2)

	cache.Put(1, 1)
	cache.Put(2, 2)
	if cache.Get(1) != 1 {
		t.Errorf("Expected 1, got %d", cache.Get(1))
	}

	cache.Put(3, 3) // 淘汰 key 2
	if cache.Get(2) != -1 {
		t.Errorf("Expected -1, got %d", cache.Get(2))
	}

	cache.Put(4, 4) // 淘汰 key 1
	if cache.Get(1) != -1 {
		t.Errorf("Expected -1, got %d", cache.Get(1))
	}
	if cache.Get(3) != 3 {
		t.Errorf("Expected 3, got %d", cache.Get(3))
	}
	if cache.Get(4) != 4 {
		t.Errorf("Expected 4, got %d", cache.Get(4))
	}
}