URLCatche缓存机制-前端实现

￡神魔★判官ぃ 2022-09-05 12:37 148阅读 0赞

## 今天是学习前端的第391天，学习了一下在牛客看到同学的URLCatche缓存写的十分的有意思就研究了一下，并可以加强我们对指针的学习。 ##

## URLCatche大概含义就是个具有一定长度的储存卡，首先设置上长度size，存储put的长度超过限制后会将最开始存储的数据删除掉，获取get数据后数据会放到首位。 ##

## 这是一个空URLCatche ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21tbW1tbW1tbW16_size_16_color_FFFFFF_t_70]

## 存入一条数据后 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21tbW1tbW1tbW16_size_16_color_FFFFFF_t_70 1]

## 使用 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21tbW1tbW1tbW16_size_16_color_FFFFFF_t_70 2]

# 源码放在下面： #

class ListNode { 
      constructor(key, val) { 
        this.key = key
        this.val = val
        this.pre = null
        this.next = null
      }
    }
    
    var LRUCache = function (capacity) { 
      this.size = capacity
      this.map = new Map()
      this.head = new ListNode(null, null)
      this.tail = new ListNode(null, null)
      this.head.next = this.tail
      this.tail.pre = this.head
    }
    
    LRUCache.prototype.get = function (key) { 
      if (!this.map.has(key)) return -1
      const val = this.map.get(key).val
      this.put(key, val)
      return val
    }
    
    LRUCache.prototype.put = function (key, value) { 
      if (!this.map.has(key)) { 
        if (this.map.size === this.size) { 
          let node = this.tail.pre
          const k = node.key
          this.tail.pre = node.pre
          node.pre.next = this.tail
          node.pre = null
          node.next = null
          node = null
          this.map.delete(k)
        }
        const node = new ListNode(key, value)
        node.next = this.head.next
        node.pre = this.head
        node.next.pre = node
        node.pre.next = node
        this.map.set(key, node)
      } else { 
        const node = this.map.get(key)
        node.val = value
        if (node.pre !== this.head) { 
          node.pre.next = node.next
          node.next.pre = node.pre
          node.pre = this.head
          node.next = this.head.next
          node.pre.next = node
          node.next.pre = node
        }
      }
    }
    const cache = new LRUCache(2)
    cache.put('a', 123)
    cache.put('b', 456)
    cache.put('c', 789)

#### 照抄自：[牛客同学货拉拉面经][Link 1] ####

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21tbW1tbW1tbW16_size_16_color_FFFFFF_t_70]: /images/20220829/879ffe9875494858b291450035f658f1.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21tbW1tbW1tbW16_size_16_color_FFFFFF_t_70 1]: /images/20220829/c9bdd2325dce4a5d86f4532adf540f9a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21tbW1tbW1tbW16_size_16_color_FFFFFF_t_70 2]: /images/20220829/5de0747dc2bb4b1ab6a1ff7ae055efb7.png
[Link 1]: https://www.nowcoder.com/discuss/702800?source_id=discuss_experience_nctrack&channel=-1