给定一个排序链表，删除所有重复的元素，使得每个元素只出现一次。
示例 1:
输入: 1->1->2
输出: 1->2
示例 2:
输入: 1->1->2->3->3
输出: 1->2->3
代码
class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
if (!head || !head->next) return head;
ListNode *start = head;
while (start && start->next) {
if (start->val == start->next->val) {
ListNode *tmp = start->next;
start->next = start->next->next;
delete tmp;
} else start = start->next;
}
return head;
}
};
