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| public class Solution {
public ListNode detectCycle(ListNode head) {
if (head == null || head.next == null) return null;
ListNode slow = head, fast = head;
while (fast != null && fast.next != null) {
fast = fast.next.next;
slow = slow.next;
if (slow == fast) break;
}
if (fast == null || fast.next == null) return null;
slow = head;
while (fast != slow) {
fast = fast.next;
slow = slow.next;
}
return slow;
}
}
|