#Linked List

Explain how to convert a sorted linked list into a height-balanced binary search tree (BST). Discuss your approach and the time complexity involved.

Given a linked list `1 → 2 → 3 → 4 → 5`, reverse the nodes in pairs to obtain `2 → 1 → 4 → 3 → 5`.

Reverse a linked list in pairs. For example, given the input 1 → 2 → 3 → 4 → 5, the output should be 2 → 1 → 4 → 3 → 5.

Implement an algorithm to detect a loop in a linked list. Consider edge cases in your approach.

Given a linked list with a cycle, write a method to find and return the node at which the cycle begins. Discuss the logic behind your approach, including any flowchart or diagram if necessary.