NC93 设计LRU缓存结构

https://www.nowcoder.com/practice/e3769a5f49894d49b871c09cadd13a61

第一次解：

参考自： https://geektutu.com/post/geecache-day1.html

package main

import "container/list"

type Cache struct {
    c map[int]*list.Element
    ll *list.List
    mem int
    max int
}

type entry struct {
    key   int
    value int
}

func (r *Cache) Get(key int) int {
    if ele, ok := r.c[key]; ok {
        r.ll.MoveToFront(ele)
        kv := ele.Value.(*entry)
        return kv.value
    }
    
    return -1
}

func (r *Cache) RemoveOld() {
    ele := r.ll.Back()
    if ele != nil {
        r.ll.Remove(ele)
        kv := ele.Value.(*entry)
        delete(r.c, kv.key)
        r.mem--
    }
}

func (r *Cache) Set(key, value int) {
    if ele, ok := r.c[key]; ok {
        r.ll.MoveToFront(ele)
        kv := ele.Value.(*entry)
        kv.value = value
    } else {
        ele := r.ll.PushFront(&entry{key, value})
        r.c[key] = ele
        r.mem++
    }
    
    if r.max != 0 && r.mem > r.max {
        r.RemoveOld()
    }
}

/**
 * lru design
 * @param operators int整型二维数组 the ops
 * @param k int整型 the k
 * @return int整型一维数组
*/
func LRU(operators [][]int, k int) []int {
    var result []int
    cache := &Cache{
        c:   make(map[int]*list.Element),
        ll:  list.New(),
        mem: 0,
        max: k,
    }

    for _, arr := range operators {
        if arr[0] == 1 {
            cache.Set(arr[1], arr[2])
        } else if arr[0] == 2 {
            result = append(result, cache.Get(arr[1]))
        }
    }

    return result
}