declare class Stack<T> {
    private _stack;
    constructor();
    /**
     * Push a value onto the stack and return the new size of the stack
     *
     * O(1)
     * @param value the value to add to the stack.
     * @returns the new size of the stack.
     */
    push(value: T): number;
    /**
     * Pop a value from the stack and return it. Returns undefined if empty.
     *
     * O(1)
     * @returns the top value from the stack or undefined if the stack is empty.
     */
    pop(): T | undefined;
    /**
     * Return the top value from the stack without removing it. Returns undefined
     * if the stack is empty.
     *
     * O(1)
     * @returns the top value from the stack or undefined if the stack is empty.
     */
    peek(): T | undefined;
    /**
     * Remove all elements from the stack.
     *
     * O(1)
     */
    clear(): void;
    /**
     * Return the current number of elements in the stack.
     *
     * O(1).
     */
    get length(): number;
}
export default Stack;