#Leetcode# 82. Remove Duplicates from Sorted List II

https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

Example 1:

Input: 1->2->3->3->4->4->5
Output: 1->2->5

Example 2:

Input: 1->1->1->2->3
Output: 2->3

代码：

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        if(!head || !head ->next) return head;
        ListNode *dummy = new ListNode(-1), *pre = dummy;
        dummy -> next = head;
        while(pre -> next) {
            ListNode *cur = pre -> next;
            while(cur -> next && cur -> val == cur -> next -> val)
                cur = cur -> next;
            
            if(cur != pre -> next) pre -> next = cur -> next;
            else pre = pre -> next;
        }
        return dummy ->next;
    }
};

　　有可能头结点就是重复的是要被删除的 所以要 dummy 

FHFHFH