Remove missing file + Add LRU Cache implementation

javascript/lru-cache.js

@@ -0,0 +1,67 @@
+// lru-cache.js
+// Tiny LRU cache with O(1) get/put using Map (insertion order).
+// API: get/put/has/delete/clear/size. Returns -1 on miss to match your original.
+
+export class LRUCache {
+  /**
+   * @param {number} capacity - max number of entries (>=1)
+   */
+  constructor(capacity) {
+    if (!Number.isInteger(capacity) || capacity < 1) {
+      throw new Error("capacity must be an integer >= 1");
+    }
+    this.capacity = capacity;
+    this.cache = new Map(); // key -> value (MRU at the end)
+  }
+
+  /**
+   * @param {any} key
+   * @returns {any} value or -1 if not found
+   */
+  get(key) {
+    if (!this.cache.has(key)) return -1;
+    const value = this.cache.get(key);
+    // move to MRU
+    this.cache.delete(key);
+    this.cache.set(key, value);
+    return value;
+  }
+
+  /**
+   * @param {any} key
+   * @param {any} value
+   */
+  put(key, value) {
+    if (this.cache.has(key)) this.cache.delete(key);
+    this.cache.set(key, value);
+    if (this.cache.size > this.capacity) {
+      // evict LRU (first key)
+      const lruKey = this.cache.keys().next().value;
+      this.cache.delete(lruKey);
+    }
+  }
+
+  /**
+   * @param {any} key
+   * @returns {boolean}
+   */
+  has(key) {
+    return this.cache.has(key);
+  }
+
+  /**
+   * @param {any} key
+   * @returns {boolean}
+   */
+  delete(key) {
+    return this.cache.delete(key);
+  }
+
+  clear() {
+    this.cache.clear();
+  }
+
+  get size() {
+    return this.cache.size;
+  }
+}