/**
 * Represents a priority queue data structure.
 * @template T The type of elements in the priority queue.
 * @example
 * const pq = new PriorityQueue<string>();
 * pq.enqueue('task1', 2).enqueue('task2', 1);
 * console.log(pq.dequeue()); // 'task2'
 */
export declare class PriorityQueue<T> {
    private items;
    /**
     * Adds an item to the priority queue with the specified priority.
     * @param {T} item - The item to add to the priority queue.
     * @param {number} priority - The priority of the item (lower numbers indicate higher priority). Default: 1
     * @returns {PriorityQueue<T>} The priority queue instance for chaining.
     */
    enqueue(item: T, priority?: number): PriorityQueue<T>;
    private bubbleUp;
    /**
     * Removes and returns the item with the highest priority from the queue.
     * @returns {T} The item with the highest priority, or undefined if the queue is empty.
     * @throws {Error} If the priority queue is empty.
     */
    dequeue(): T;
    private bubbleDown;
    /**
     * Returns the number of items in the priority queue.
     * @returns {number} The size of the priority queue.
     */
    size(): number;
    /**
     * Checks if the priority queue is empty.
     * @returns {boolean} True if the priority queue is empty, false otherwise.
     */
    isEmpty(): boolean;
    /**
     * Returns the item with the highest priority without removing it.
     * @returns {T | undefined} The item with the highest priority, or undefined if the queue is empty.
     */
    peek(): T | undefined;
    /**
     * Checks if the priority queue contains a specific item.
     * @param {T} item - The item to check for.
     * @returns {boolean} True if the item is in the priority queue, false otherwise.
     */
    contains(item: T): boolean;
    /**
     * Changes the priority of an existing item.
     * @param {T} item - The item whose priority is to be changed.
     * @param {number} newPriority - The new priority for the item.
     * @returns {boolean} True if the priority was changed, false if the item was not found.
     */
    changePriority(item: T, newPriority: number): boolean;
    /**
     * Removes a specific item from the priority queue.
     * @param {T} item - The item to remove.
     * @returns {T | boolean} The Value of the removed item if the item was removed, false otherwise.
     */
    remove(item: T): T | boolean;
    /**
     * Merges another priority queue into this one.
     * @param {PriorityQueue<T>} otherQueue - The other priority queue to merge.
     */
    merge(otherQueue: PriorityQueue<T>): void;
    /**
     * Serializes the priority queue to a JSON string.
     * @returns {string} The serialized priority queue.
     */
    serialize(): string;
    /**
     * Deserializes a JSON string to populate the priority queue.
     * @param {string} data - The JSON string to deserialize.
     */
    deserialize(data: string): void;
}