[Leetcode]83. 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

.

/**
* 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 == NULL || head->next == NULL)
return head;
ListNode* p = head;
ListNode* q = p->next;
while (q != NULL)
{
if (p->val == q->val)
{
q = q->next;
p->next = q;
}
else
{
p = p->next;
q = q->next;
}
}
return head;
}
};