Detect The Cycle

Kevin has given you a Singly Linked List that contains only integers. You have to determine if it forms a cycle or not.

A cycle occurs when a node's next pointer points back to a previous node in the list.

Input format :

The first line of each test case contains the elements of the singly linked list separated by a single space and terminated by -1 and hence -1 would never be a list element.

The second line contains the integer position 'POS' that represents the position (0-indexed) in the linked list where the tail connects to. If 'POS' is -1, then there is no cycle in the linked list.

Output format :

The only line of output contains 'true' if the linked list has a cycle or 'false' otherwise.

You don't have to explicitly print by yourself. It has been taken care of.

Follow Up:

Try to solve this problem in O(N) Time Complexity and O(1) space Complexity.

Constraints :

0 <= N <= 10^6
-1 <= POS < N
-10^9 <= DATA <= 10^9 and DATA != -1

Where 'N' is the size of the singly linked list, 'POS' represents the position (0-indexed) in the linked list where the tail connects to and 'DATA' is the Integer data of the singly linked list.

Time Limit: 1 sec