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fix #844 #846

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Nov 25, 2021
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83 changes: 17 additions & 66 deletions Cache/LRUCache.js
Original file line number Diff line number Diff line change
@@ -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
}
}

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