merge: fix TheAlgorithms#844 (TheAlgorithms#846)

* fix TheAlgorithms#844 * formatted code according to standard.js

Author: aditya1944

Cache/LRUCache.js

@@ -1,88 +1,39 @@
-class DoubleLinkedListNode {
- // Double Linked List Node built specifically for LRU Cache
- constructor (key, val) {
- this.key = key
- this.val = val
- this.next = null
- this.prev = null
- }
-}
-
-class DoubleLinkedList {
- // Double Linked List built specifically for LRU Cache
- constructor () {
- this.head = new DoubleLinkedListNode(null, null)
- this.rear = new DoubleLinkedListNode(null, null)
- this.head.next = this.rear
- this.rear.prev = this.head
- }
-
- add (node) {
- // Adds the given node to the end of the list (before rear)
- const temp = this.rear.prev
- temp.next = node
- node.prev = temp
- this.rear.prev = node
- node.next = this.rear
- }
-
- remove (node) {
- // Removes and returns the given node from the list
- const tempLast = node.prev
- const tempNext = node.next
- node.prev = null
- node.next = null
- tempLast.next = tempNext
- tempNext.prev = tempLast
-
- return node
- }
-}
-
 class LRUCache {
  // LRU Cache to store a given capacity of data
  constructor (capacity) {
- this.list = new DoubleLinkedList()
+ this.cache = new Map()
  this.capacity = capacity
- this.numKeys = 0
  this.hits = 0
  this.miss = 0
- this.cache = {}
  }
 
  cacheInfo () {
  // Return the details for the cache instance [hits, misses, capacity, current_size]
- return `CacheInfo(hits=${this.hits}, misses=${this.miss}, capacity=${this.capacity}, current size=${this.numKeys})`
+ return `CacheInfo(hits=${this.hits}, misses=${this.miss}, capacity=${this.capacity}, current size=${this.cache.size})`
  }
 
  set (key, value) {
- // Sets the value for the input key and updates the Double Linked List
- if (!(key in this.cache)) {
- if (this.numKeys >= this.capacity) {
- const keyToDelete = this.list.head.next.key
- this.list.remove(this.cache[keyToDelete])
- delete this.cache[keyToDelete]
- this.numKeys -= 1
- }
- this.cache[key] = new DoubleLinkedListNode(key, value)
- this.list.add(this.cache[key])
- this.numKeys += 1
- } else {
- const node = this.list.remove(this.cache[key])
- node.val = value
- this.list.add(node)
+ // Sets the value for the input key and if the key exists it updates the existing key
+ if (this.cache.size === this.capacity) {
+ // delete oldest key existing in map
+ this.cache.delete(this.cache.keys().next().value)
  }
+ this.cache.set(key, value)
  }
 
  get (key) {
- // Returns the value for the input key and updates the Double Linked List. Returns null if key is not present in cache
- if (key in this.cache) {
+ // Returns the value for the input key. Returns null if key is not present in cache
+ if (this.cache.has(key)) {
+ const value = this.cache.get(key)
+ // refresh the cache to update the order of key
+ this.cache.delete(key)
+ this.cache.set(key, value)
  this.hits += 1
- this.list.add(this.list.remove(this.cache[key]))
- return this.cache[key].val
+ return value
+ } else {
+ this.miss += 1
+ return null
  }
- this.miss += 1
- return null
  }
 }