反转链表

输入一个链表，反转链表后，输出新链表的表头。

个人思路：一个一个断链，断链之间用指针记录下。

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode ReverseList(ListNode head) {
        if(head==null)
            return null;
        else if(head.next==null)
            return head;
        else{
            ListNode p = head.next;
            ListNode temp = head;
            head = head.next;
            temp.next = null;
            while(head.next!=null){
                head = head.next;
                p.next = temp;
                temp = p;
                p = head;
            }
            head.next = temp;
            return head;
        }

    }
}