Leetcode - Linked List Cycle

Given a linked list, determine if it has a cycle in it.
  Use fast and low pointer. The advantage about fast/slow pointers is that when a circle is located, the fast one will catch the slow one for sure.

    public boolean hasCycle(ListNode head) {
        ListNode fast = head;
        ListNode slow = head;
 
        if(head == null)
            return false;
 
        if(head.next == null)
            return false;
 
        while(fast != null && fast.next != null){
            slow = slow.next;
            fast = fast.next.next;
 
            if(slow == fast)
                return true;
        }
 
        return false;
    }

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