C/C ++ test questions

1. General function declaration:
Node fun (node * head, int index) requires us to implement the methods in the function.
Node is a one-way linked list.
Function to be implemented: return the nth node to which the last part belongs.
How to optimize it depends on how we use it ~

Generally, two pointers P1 and P2 are set.
First, both P1 and P2 point to the head
Then P2 goes forward to n steps, so that there are n nodes separated between P1 and P2.
Then P1 and P2 move forward at the same time. When P2 reaches the last node, P1 is the last n nodes.