lintcode-easy-Remove Duplicates from Sorted List

Given a sorted linked list, delete all duplicates such that each element appear only once.

Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.

/**
 * Definition for ListNode
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param ListNode head is the head of the linked list
     * @return: ListNode head of linked list
     */
    public static ListNode deleteDuplicates(ListNode head) { 
        // write your code here
        if(head == null || head.next == null)
            return head;
        
        ListNode new_head = new ListNode(head.val);
        ListNode p1 = new_head;
        ListNode p2 = head.next;
        
        while(p2 != null){
            if(p2.val == p1.val){
                p2 = p2.next;
            }
            else{
                p1.next = new ListNode(p2.val);
                p1 = p1.next;
                p2 = p2.next;
            }
        }
        
        return new_head;
    }  
}