You are tasked with simulating the history of web page visits in a browser. Implement the BrowserHistory class to manage visit, back, and forward actions.
You are given two linked lists: list1 and list2 with sizes n and m respectively. The task is to remove the nodes from position a to position b in list1 and replace them with list2. Return the head of the modified list.
Design a queue that supports operations at the front, middle, and back. Implement the FrontMiddleBackQueue class with methods for adding and removing elements from these positions.
You are given a singly linked list and an integer k. The task is to swap the values of the kth node from the beginning of the list with the kth node from the end of the list. The list is 1-indexed.
You are tasked with creating an authentication system that handles tokens. Each token has an expiration time, and a user can generate new tokens or renew existing ones before they expire. The system should track and count the number of unexpired tokens at any given time.
In a linked list, a critical point is defined as either a local maxima or a local minima. A local maxima is when a node’s value is strictly greater than both its previous and next node, while a local minima is when a node’s value is strictly smaller than both its previous and next node. Given a linked list, return an array containing the minimum and maximum distances between any two distinct critical points. If there are fewer than two critical points, return [-1, -1].