[Leetcode]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

.

思路，两个指针，pre和cur。pre指向当前指针的前一个指针，用dump头节点来解决corner case问题。当有重复的时候cur一直往前知道没有重复的地方，然后pre指向没有重复的新值，更新pre和cur。

public ListNode deleteDuplicates(ListNode head) {
if (head == null) {
return head;
}

ListNode dump = new ListNode(0);
dump.next = head;
ListNode pre = dump;
ListNode cur = pre.next;
while (cur != null && cur.next != null) {
if (cur.val == cur.next.val) {
cur = cur.next;
} else {
pre.next.next = cur.next;
pre = cur;
cur = cur.next;
}
}
pre.next.next = cur.next;
return dump.next;
}