206. Reverse Linked List

Reverse a singly linked list.

click to show more hints.

Subscribe to see which companies asked this question

这是我以前乱写的……其实不能用这种空间复杂度高的

/** * 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) {       List<Integer>  list = new ArrayList<Integer>();       for(ListNode a = head;a!=null;a=a.next){           list.add(a.val);       }       int i = list.size()-1;       for(ListNode a = head;a!=null;a=a.next){           a.val=list.get(i);i--;       }       return head;    }}