83. 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; }
 * }
 */

class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode list = head;
        /*
        此时list对象相当于head对象的引用，所以改变list指针会改变head，
        因为它们指针是同一个，而改变val则不会改变head
        */
        while(list != null && list.next != null){
            if(list.next.val == list.val)
                list.next =list.next.next;//相应的会改变head
            else
                list = list.next;   //不会改变head,但会改变list，用一次减少一个元素
        }
        return head; //所以return list 是错误的
    }
}

/*
ArrayList<Integer> arrayList =new ArrayList<>();
    for (int i = 0; i < 5; i++) {
        arrayList.add(i);
    }

    ArrayList<Integer> bArrayList =arrayList;
    System.out.println(bArrayList);
    bArrayList.add(5);
    System.out.println(arrayList);
    System.out.println(bArrayList);
*/