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)    return NULL;        ListNode *cur = head;        ListNode *next = head->next;        while(next != NULL)        {            if(next->val == cur->val)            {                cur->next = next->next;                delete next;                next = cur->next;            }            else            {                cur = cur->next;                next = next->next;            }        }        return head;    }};