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) {
if (head==null || head.next==null) {
return head;
}
ListNode pre = null;
ListNode cur = head;
ListNode nex = null;
while (head != null) {
nex = head.next;
head.next = pre;
pre = head;
head = nex;
}
return pre;
}
}