Create 0460-lfu-cache.js

Author: jaliph

javascript/0460-lfu-cache.js

@@ -0,0 +1,121 @@
+// https://leetcode.com/problems/lfu-cache/
+
+class ListNode {
+  constructor(val, next, prev) {
+    this.val = (val===undefined ? 0 : val)
+    this.next = (next===undefined ? null : next)
+    this.prev = (next===undefined ? null : prev)
+  }
+}
+
+class LinkedList {
+  constructor() {
+    this.map = new Map()
+    this.Right = new ListNode(null)
+    this.Left = new ListNode(null, this.Right)
+    this.Right.prev = this.Left
+  }
+
+  len() {
+    return this.map.size
+  }
+
+  pop(val) {
+    if (this.map.has(val)) {
+      let node = this.map.get(val)
+
+      // save
+      let prevNode = node.prev
+      // delete
+      prevNode.next = node.next
+      prevNode.next.prev = prevNode
+      this.map.delete(val)
+    }
+  }
+
+  popleft() {
+    let data = this.Left.next.val
+    this.Left.next = this.Left.next.next
+    this.Left.next.prev = this.Left
+    this.map.delete(data)
+    return data
+  }
+
+  pushRight(val) {
+    let newNode = new ListNode(val, this.Right)
+    newNode.prev = this.Right.prev
+    newNode.prev.next = newNode
+    this.Right.prev = newNode
+    this.map.set(val, newNode)
+  }
+
+  update(val) {
+    this.pop(val)
+    this.pushRight(val)
+  }
+}
+
+/**
+ * @param {number} capacity
+ */
+var LFUCache = function(capacity) {
+  this.capacity = capacity
+  this.valueMap = new Map()
+  this.countMap = new Map()
+  this.lftCount = 1
+  this.lists = []
+  this.counter = (key) => {
+    let count = this.countMap.get(key) || 0
+    if (this.lists[count]) {
+      this.lists[count].pop(key)
+    }
+    if (!this.lists[count + 1]) {
+      this.lists[count + 1] = new LinkedList()
+    }
+    this.lists[count + 1].pushRight(key)
+    this.countMap.set(key, count + 1)
+    // console.log(this.lftCount == count, count, this.lists[count].len())
+    if (this.lftCount == count && this.lists[count] && this.lists[count].len() === 0) {
+      this.lftCount++
+    }
+  }
+};
+
+/** 
+ * @param {number} key
+ * @return {number}
+ */
+LFUCache.prototype.get = function(key) {
+  if (!this.valueMap.has(key)) {
+    return -1
+  }
+  
+  this.counter(key)
+  return this.valueMap.get(key)
+};
+
+/** 
+ * @param {number} key 
+ * @param {number} value
+ * @return {void}
+ */
+LFUCache.prototype.put = function(key, value) {
+
+  if (!this.valueMap.has(key) && this.valueMap.size == this.capacity) {
+    // we need to evict
+    // console.log(this.lists[this.lftCount])
+    let evictedKey = this.lists[this.lftCount].popleft()
+    this.valueMap.delete(evictedKey)
+    this.countMap.delete(evictedKey)
+  }
+
+  this.valueMap.set(key, value)
+  this.counter(key)
+  this.lftCount = Math.min(this.countMap.get(key), this.lftCount)
+};
+/** 
+ * Your LFUCache object will be instantiated and called as such:
+ * var obj = new LFUCache(capacity)
+ * var param_1 = obj.get(key)
+ * obj.put(key,value)
+ */