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

需要注意的是在第二个while循环里应该限制cur != null，避免nullPoint

/**
* 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 dummy = new ListNode(0);
dummy.next = head;
ListNode prev = dummy;
ListNode cur = head;
while(cur != null && cur.next != null) {
if (cur.val == cur.next.val) {
int dupVal = cur.val;
prev = cur;
cur = cur.next;
while (cur != null && cur.val == dupVal){
prev.next = cur.next;
cur = cur.next;
}
}
else {
prev = cur;
cur = cur.next;
}
}
return dummy.next;
}
}