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.

程式碼

 public static ListNode deleteDuplicates(ListNode head) {
	        if (head==null || head.next==null) return head; 
	        ListNode first = head;
	        ListNode second=head.next;
	        while(second!=null){
	            if(first.val==second.val){
	                second=second.next;
	                first.next=second;
	            }	            
	            else{
	            	  first=first.next;
	            	  second=first.next;	            		
	            }
	            
	        }
	        
	        return head;
	    }