Remove Duplicates from Sorted List

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

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

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { *         val = x; *         next = null; *     } * } */public class Solution {    public ListNode deleteDuplicates(ListNode head) {        if(head==null) return null;        ListNode slow=head;        ListNode fast=head;        while(fast!=null){            if(slow.val!=fast.val){                slow.next=fast;                slow=slow.next;            }            fast=fast.next;        }        slow.next=null;        return head;    }}