链表

链表逆置

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    public ListNode ReverseList (ListNode head) {
        // write code here
        ListNode pre = null;
        ListNode cur = head;
        while(cur!=null){
            ListNode next= cur.next;
            cur.next = pre;
            pre = cur;
            cur = next;
        }
        return pre;
    }
}

链表有环

https://www.cnblogs.com/chenyi502/p/17494929.html