2.1 --- remove duplicates from unsorted linked List

Q:
2.1
Write code to remove duplicates from an unsorted linked list.
FOLLOW UP
How would you solve this problem if a temporary buffer is not allowed?

A:
Using hash table
（没想到，或者想到了，但是以前没有做过，故而不知道去搞）

 public static void deleteDuplicates(LinkList list){
  Hashtable table  = new Hashtable();
  Node pointer = list.head;
  Node prePointer = null;
  while(pointer != null){
   if(table.containsKey(pointer.data))
    prePointer.next = pointer.next;
   else{
    table.put(pointer.data, true);
   }
   prePointer = pointer;
   pointer = pointer.getNext();
  }
 }
 public static void deleteDuplicatesNoBuffer(LinkList list){
  // use two pointers to delete duplicates
  Node curPointer = list.head;
  Node runner = null;
  Node preRunner = null;
  while(curPointer != null){
   preRunner = curPointer;
   runner = curPointer.next;
   // check if all has the same value
   while(runner!= null){
    if(runner.data == curPointer.data){
     // delete the at position runner. 
     preRunner.next = runner.next;
    }else{
     preRunner = runner;     
    }
    runner = runner.next;
   }   
   curPointer = curPointer.next;
  }
  
 } 

Mistakes:

1: 在list iterate的时候， 经常忘记，update指针，使之指向下一个位置。