/**
knakul853
 */
class Solution {
public:
    bool hasCycle(ListNode *head) { // for removing the node find starting node of the loop and set it's next as null.

        if( !head || !head->next ) return false;

        ListNode* slow = head;
        ListNode* fast = head->next;

        while(slow != fast )
        {
            if( !fast || !fast->next ) return false;

            slow = slow->next;
            fast = fast->next->next;
        }

        return true;
    }
};