[lintcode easy]Reserve Linked list

Reverse Linked List

Reverse a linked list.

 

 

Example

For linked list 1->2->3, the reversed linked list is 3->2->1

Challenge

Reverse it in-place and in one-pass

 

use two pointer to record the current node and previous node.

 

/**
 * Definition for ListNode.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int val) {
 *         this.val = val;
 *         this.next = null;
 *     }
 * }
 */ 
public class Solution {
    /**
     * @param head: The head of linked list.
     * @return: The new head of reversed linked list.
     */
    public ListNode reverse(ListNode head) {
     
      ListNode cur=head;
      ListNode prev=null;
      
      while(cur!=null)
      {
           ListNode next=cur.next;
           cur.next=prev;
           prev=cur;
           cur=next;
      }
      return prev;
    }

}