public boolean isCircle() { if(first == null || first.next == null) return false; Node<U> slow = first; Node<U> fast = first.next; int i = 1; while (fast != null && fast.next != null) { if(fast.equals(slow)) { System.out.println("开始结束:"+(i++)+",slow="+slow.unit+",fast="+fast.unit); return true; } System.out.println("开始循环:"+(i++)+",slow="+slow.unit+",fast="+fast.unit); slow = slow.next; fast = fast.next.next; } return false; }
这个代码是判断是否环形链表的方法,一定会相遇,因为它们的距离每一次执行完后fast与slow就减1,最终为0相遇。当链表如下时,代码运行输出:
输出:
开始循环:1,slow=0,fast=1
开始循环:2,slow=1,fast=3
开始循环:3,slow=2,fast=5
开始循环:4,slow=3,fast=1
开始循环:5,slow=4,fast=3
开始结束:6,slow=5,fast=5
true