剑指Offer-链表反转（Java)

题目：实现单链表的反转

1→2→3→4→5

5→4→3→2→1

/*
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=null;
        ListNode cur=head;
        while(head!=null){
            head=head.next;
            cur.next=pre;
            pre=cur;
            cur=head;
        }
       return pre;
    }
}