[leetcode] 82. Remove Duplicates from Sorted List II 解题报告

题目链接：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.

For example,

Given

1->2->3->3->4->4->5

, return

1->2->5

.

Given

1->1->1->2->3

, return

2->3

.

思路：创建一个虚拟头结点可以为操作带来极大的遍历，然后就是如果发现重复元素，则开始判断以后的是不是等于这个元素，是的话都删掉。不是的话就遍历下一个。
代码如下：

/**
* 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) return head;
ListNode *pHead = new ListNode(0), *p=pHead, *q;
pHead->next = head;
int val = head->val;
while(p)
{
q = p->next;
if(q && q->next && q->val == q->next->val)
{
int val = q->val;
while(q && q->val == val)
{
p->next = q->next;
delete q;
q = p->next;
}
}
else p = p->next;
}
head = pHead->next;
delete pHead;
return head;
}
};