铭记:
源码下载
141. 环形链表
代码
public boolean hasCycle(ListNode head) {
if (head == null || head.next == null) {
return false;
}
ListNode slow = head;
ListNode fast = head.next;
while (slow != null && fast != null) {
if (slow == fast) {
return true;
}
// 每次循环慢指针走1步
slow = slow.next;
// 每次循环快指针走2步
if (fast.next != null) {
fast = fast.next.next;
}
else {
fast = null;
}
}
return false;
}
