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