反转一个单链表。
示例:
输入: 1->2->3->4->5->NULL
输出: 5->4->3->2->1->NULL
进阶:
你可以迭代或递归地反转链表。你能否用两种方法解决这道题?
以下为迭代解法:
class Solution {
public ListNode reverseList(ListNode head) {
ListNode prev = null;
ListNode cur = head;
while(cur != null){
ListNode tempNode = cur.next;
cur.next = prev;
prev = cur;
cur = tempNode;
}
return prev;
}
以下为递归解法:
class Solution {
public ListNode reverseList(ListNode head) {
if(head == null || head.next == null){
return head;
ListNode cur = reverseList(head.next);
head.next.next = head;
head.next = null;
return cur;
}