141. Linked List Cycle (LL)
1 class Solution { 2 public boolean hasCycle(ListNode head) { 3 if(head == null) return false; 4 if(head.next == null) return false; 5 ListNode node1 = head; 6 ListNode node2 = head; 7 while(node1.next != null) { 8 node1 = node1.next; 9 if(node2.next != null && node2.next.next != null) { 10 node2 = node2.next.next; 11 }else { 12 return false; 13 } 14 if(node1 == node2) { 15 return true; 16 } 17 } 18 return false; 19 } 20 }
一个快一个慢 要是重合了就有cycle