The language is C.

Implement a function that detects if there is a loop in a singly linked list. A loop is defined as a link from one node to itself or to another node that is before the node in the list. The function may only make one pass through the list. It must return 1 if a loop exists; 0 otherwise. Be sure to test your function! You may start with code that you have written for other labs. This is a common interview question!