Length of the loop

Problem: given a first unidirectional pointer linked list, if there is a ring, the length of the loop is returned, otherwise 0.

Ideas: the use of two hands, the moving speed of a fast and slow, fast if the tail pointer reaches the first, no ring, if slow pointer quickly catch up with the pointer, the pointer to walk the length of a fast loop.

java code:

	int getCircleLength(ListNode head){
        ListNode slow=head;
        if(slow==null||slow.next==null)
            return 0;
        ListNode fast=slow.next.next;
        while(fast!=null&&fast.next!=null){
            if(slow==fast)
                return getLength(slow);
            slow=slow.next;
            fast=fast.next.next;
        }
        return 0;
    }
    
    int getLength(ListNode node){
        int length=1;
        ListNode curr=node;
        while(curr.next!=node){
            length++;
            curr=curr.next;
        }
        return length;
    }