Method push

src/04-stack/stack.ts:11–13

* Pushes an item onto the top of the stack. * @param item - The item to push * @complexity Time O(1) | Space O(1)

(item: T)

   * @complexity Time O(1) | Space O(1)
   */
  push(item: T): void {
    this.items.push(item);
  }

  /**
   * Removes and returns the top item; returns undefined if empty.