https://leetcode.com/problems/remove-duplicates-from-sorted-list/?tab=Description
注意dummy node的使用。
class Solution {
public:
ListNode* deleteDuplicates(ListNode* head) {
if (!head || !head->next) return head;
ListNode dummy(0); dummy.next = head;
while (head) {
ListNode *p = head->next;
while (p && p->val == head->val) {
p = p->next;
head->next = p;
}
head = p;
}
return dummy.next;
}
};