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?
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/reverse-linked-list
迭代
public ListNode reverseList(ListNode head) {
ListNode pre = null;
ListNode cur = head;
while(cur != null){
ListNode temp = cut.next;
cur.next = pre;
pre = cur;
cur = temp;
}
return pre;
}
递归
public ListNode reverseList(ListNode head) {
if(head == null || head.next == null){
return head;
}
ListNode pre = reverseList(head.next);
head.next.next = head;
head.next = null;
return pre;
}