go实现LRU

package main

import "fmt"

type LRUCache struct {
	length int
	cap    int
	cache  map[interface{}]*DoubleLinkNode
	head   *DoubleLinkNode
	tail   *DoubleLinkNode
}

// 双链表节点
// 头节点和尾节点不存数据，方便处理
type DoubleLinkNode struct {
	pre   *DoubleLinkNode
	next  *DoubleLinkNode
	key   interface{}
	value interface{}
}

func (lru *LRUCache) Get(key interface{}) interface{} {
	if _, ok := lru.cache[key]; !ok {
		return -1
	}

	node := lru.cache[key]
	lru.moveNodeToHead(node)
	return node.value
}

func (lru *LRUCache) Put(key interface{}, value interface{}) {
	if node, ok := lru.cache[key]; !ok {
		newNode := &DoubleLinkNode{
			key:   key,
			value: value,
		}

		if lru.length == lru.cap {
			tailPre := lru.tail.pre
			lru.removeNode(tailPre)
			delete(lru.cache, tailPre.key)
			lru.length--
		}

		lru.cache[key] = newNode
		lru.headInsertNode(newNode)
		lru.length++
	} else {
		node.value = value
		lru.moveNodeToHead(node)
	}
}

func (lru *LRUCache) moveNodeToHead(node *DoubleLinkNode) {
	lru.removeNode(node)
	lru.headInsertNode(node)
}

func (lru *LRUCache) removeNode(node *DoubleLinkNode) {
	node.pre.next = node.next
	node.next.pre = node.pre
}

func (lru *LRUCache) headInsertNode(node *DoubleLinkNode) {
	node.next = lru.head.next
	node.pre = lru.head

	lru.head.next.pre = node
	lru.head.next = node
}

func (lru *LRUCache) PrintLRUCache() {
	node := lru.head.next
	for node != lru.tail {
		fmt.Printf("%s:%d ", node.key, node.value)
		node = node.next
	}
	fmt.Println()
}

func NewLRUCache(cap int) *LRUCache {
	if cap < 0 {
		return nil
	}

	lru := &LRUCache{
		cap:   cap,
		cache: make(map[interface{}]*DoubleLinkNode),
		head:  &DoubleLinkNode{},
		tail:  &DoubleLinkNode{},
	}

	lru.head.next = lru.tail
	lru.tail.pre = lru.head

	return lru
}

func main() {
	lru := NewLRUCache(1)
	lru.Put("a", 1)
	lru.PrintLRUCache()
	lru.Put("b", 2)
	lru.PrintLRUCache()

	lru = NewLRUCache(3)
	lru.Put("a", 1)
	lru.Put("b", 2)
	lru.Put("c", 3)
	lru.PrintLRUCache()
	lru.Put("d", 4)
	lru.PrintLRUCache()
	lru.Get("b")
	lru.PrintLRUCache()
}