题目描述 输入一个链表，反转链表后，输出新链表的表头。
解题思路1
迭代
代码实现：
/*
public class ListNode {
int val;
ListNode next = null;
ListNode(int val) {
this.val = val;
}
}*/
public class Solution {
public ListNode ReverseList(ListNode head) {
ListNode newList = new ListNode(-1);
while(head != null) {
ListNode next = head.next;
head.next = newList.next;
newList.next = head;
head = next;
}
return newList.next;
}
}
解题思路2
递归
代码实现：
public class Solution {
public ListNode ReverseList(ListNode head) {
if(head == null || head.next == null)
return head;
ListNode next = head.next;
head.next = null;
ListNode newHead = ReverseList(next);
next.next = head;
return newHead;
}
}