题目描述
输入一个链表，反转链表后，输出新链表的表头。
迭代 使用头插法
/*
public class ListNode {int val;ListNode next = null;ListNode(int val) {this.val = val;}
}*/
public class Solution {public ListNode ReverseList(ListNode head) {ListNode first=new ListNode(-1);while(head!=null){ListNode next=head.next;head.next=first.next;first.next=head;head=next;}return first.next;}
}
使用递归
/*
public class ListNode {int val;ListNode next = null;ListNode(int val) {this.val = val;}
}*/
public class Solution {public ListNode ReverseList(ListNode head) {//使用递归if(head==null||head.next==null){return head;}ListNode next=head.next;head.next=null;ListNode newHead=ReverseList(next);next.next=head;return newHead;}
}