在n个节点的循环单列表中某个指针指向的节点之前插入一个节点的时间复杂度？

Question

I think that it is O(N) because in a circular singly list the pointer visits n nodes so that node to be inserted precedes the current node.

Have I got it right?

Answer 1

The usual traversal and insertion would take O(N) time. However, it can be done in O(1) as well, if the nodes can be modified.
Let the list look like A -> B-> C -> D -> A , we are given a pointer to C , and we have to insert E . Now, create a copy of C and insert it after C itself. The list now looks like A -> B-> C -> C(copy) -> D -> A . Now, we can modify the values of the original C node to store the values of E node, so the list now becomes A -> B-> E -> C -> D -> A . Since you've only created a node and inserted it in place, it takes O(1) time complexity.