题目

Reverse a singly linked list.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
 public ListNode reverseList(ListNode head) {
        ListNode pre = null;
        ListNode next = null;
        ListNode cur = head;
        if(head!=null){
            while(cur.next!=null){
                next = cur.next;
                cur.next = pre;
                pre =cur;
                cur = next;
            }
            cur.next =pre;
        }
        return cur;
    }
}