export declare class LRUCache<K, V> {
    private readonly cache;
    private readonly capacity;
    constructor(capacity: number);
    /**
     * Get a value by key.
     * Moves the key to the "most recently used" position if found.
     */
    get(key: K): V | undefined;
    /**
     * Insert or update a value by key.
     * If capacity is exceeded, evicts the least recently used item.
     */
    set(key: K, value: V): void;
    /**
     * Check if the cache contains a key (without updating its recency).
     */
    has(key: K): boolean;
    /**
     * Delete a specific key from the cache.
     */
    delete(key: K): boolean;
    /**
     * Clear the entire cache.
     */
    clear(): void;
    /**
     * Current number of elements in cache.
     */
    get size(): number;
    /**
     * Returns keys from least -> most recently used.
     */
    keys(): K[];
}