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) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        ListNode *cur = head, *next = NULL;        if (head) {            next = head->next;        }        while (next) {            while (next && cur->val == next->val) {                next = next->next;            }            cur->next = next;            cur = next;            if (next) {                next = next->next;            }           }        return head;    }};