Detect Cycle

Problem Statement

You’re given the pointer to the head node of a linked list. Find whether the list contains any cycle (or loop). A linked list is said to contain cycle if any node is re-visited while traversing the list. The head pointer given may be null meaning that the list is empty.

Input Format You have to complete the int HasCycle(Node* head) method which takes one argument - the head of the linked list. You should NOT read any input from stdin/console. Number of nodes in a linked list doesn't exceed 100.

Output Format Check whether the linked list has a cycle and return 1 if there is a cycle. Otherwise, return 0. Do NOT print anything to stdout/console.

Sample Input 1 --> NULL

1 --> 2 --> <--3

Sample Output 0 1

Explanation 1. First list has no cycle, hence return 0 2. Second list is shown to have a cycle, hence return 1.

Note After first solving the problem by yourself, see Floyd's cycle-finding algorithm for an efficient solution which uses O(N) time and O(1) additional memory.