学习一下快慢指针 希望做过的都学会都记住

public class Solution {
    public ListNode detectCycle(ListNode head) {
        ListNode fast = head;
        ListNode slow = head;
        
        while(fast != null && fast.next != null){
            fast = fast.next.next;
            slow = slow.next;

            if(slow == fast){
                ListNode a = head;
                ListNode b = fast;

                while(a != b){
                    a = a.next;
                    b = b.next;
                }

                return a;
            }
        }
        return null;
    }
}