Here is a nice site on which the different solutions can copied.
find loop singly linked list
This is the winner on that site
// Best solution
function boolean hasLoop(Node startNode){
Node slowNode = Node fastNode1 = Node fastNode2 = startNode;
while (slowNode && fastNode1 = fastNode2.next() && fastNode2 = fastNode1.next()){
if (slowNode == fastNode1 || slowNode == fastNode2) return true;
slowNode = slowNode.next();
}
return false;
}
This solution is "Floyd's
Cycle-Finding Algorithm" as published
in "Non-deterministic Algorithms" by
Robert W. Floyd in 1967. It is also
called "The Tortoise and the Hare
Algorithm".