反转链表

题目描述
输入一个链表，反转链表后，输出链表的所有元素。

/*
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;
            }
            ListNode pre = head;
            ListNode curr = pre.next;
            ListNode temp;

            while(curr!=null){
                temp = curr.next;
                curr.next = pre;
                pre = curr;
                curr = temp;
            }
            head.next = null;
            head = pre;
            return head;
    }
}