/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
public class Solution {
public ListNode deleteDuplicates(ListNode head) {
ListNode dummy = new ListNode(-1);
dummy.next = head;
ListNode pre = dummy;
ListNode cur = pre.next;
while (cur != null) {
while (cur.next != null && cur.val == cur.next.val) {
cur = cur.next;
}
if (pre.next != cur) {
pre.next = cur.next;
} else {
pre = pre.next;
}
cur = cur.next;
}
return dummy.next;
}
}
public ListNode deleteDuplicates(ListNode head) {
if (head == null) return null;
if (head.next != null && head.val == head.next.val) {
while (head.next != null && head.val == head.next.val) {
head = head.next;
}
return deleteDuplicates(head.next);
} else {
head.next = deleteDuplicates(head.next);
}
return head;
}
/*
if current node is not unique, return deleteDuplicates with head.next.
If current node is unique, link it to the result of next list made by recursive call. Any improvement?
*/