#312 · #708 · Insert into a Sorted Circular Linked List(循环有序列表的插入)

Given the head of a sorted circular linked list and an integer insertVal, insert the value so the list remains sorted, and return the head. The list may be empty, and insertVal may be smaller than all values or larger than all values. Constraints: the number of nodes is in [0, 5 * 10^4], -10^6 <= insertVal <= 10^6.