Add solution #146

Author: JoshCrozier

README.md

@@ -126,6 +126,7 @@
 143|[Reorder List](./0143-reorder-list.js)|Medium|
 144|[Binary Tree Preorder Traversal](./0144-binary-tree-preorder-traversal.js)|Easy|
 145|[Binary Tree Postorder Traversal](./0145-binary-tree-postorder-traversal.js)|Easy|
+146|[LRU Cache](./0146-lru-cache.js)|Medium|
 148|[Sort List](./0148-sort-list.js)|Medium|
 149|[Max Points on a Line](./0149-max-points-on-a-line.js)|Hard|
 151|[Reverse Words in a String](./0151-reverse-words-in-a-string.js)|Medium|

solutions/0146-lru-cache.js

@@ -0,0 +1,54 @@
+/**
+ * 146. LRU Cache
+ * https://leetcode.com/problems/lru-cache/
+ * Difficulty: Medium
+ *
+ * Design a data structure that follows the constraints of a Least Recently Used (LRU) cache.
+ *
+ * Implement the LRUCache class:
+ * - LRUCache(int capacity) Initialize the LRU cache with positive size capacity.
+ * - int get(int key) Return the value of the key if the key exists, otherwise return -1.
+ * - void put(int key, int value) Update the value of the key if the key exists. Otherwise,
+ *   add the key-value pair to the cache. If the number of keys exceeds the capacity from
+ *   this operation, evict the least recently used key.
+ *
+ * The functions get and put must each run in O(1) average time complexity.
+ */
+
+/**
+ * @param {number} capacity
+ */
+var LRUCache = function(capacity) {
+  this.cache = new Map();
+  this.capacity = capacity;
+};
+
+/**
+ * @param {number} key
+ * @return {number}
+ */
+LRUCache.prototype.get = function(key) {
+  if (!this.cache.has(key)) {
+    return -1;
+  }
+
+  const value = this.cache.get(key);
+  this.cache.delete(key);
+  this.cache.set(key, value);
+  return this.cache.get(key);
+};
+
+/**
+ * @param {number} key
+ * @param {number} value
+ * @return {void}
+ */
+LRUCache.prototype.put = function(key, value) {
+  if (this.cache.has(key)) {
+    this.cache.delete(key);
+  }
+  this.cache.set(key, value);
+  if (this.cache.size > this.capacity) {
+    this.cache.delete(this.cache.keys().next().value);
+  }
+};