Remove Duplicates from Sorted List

/**
 * 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 *lt=head;
        ListNode *cur=lt->next;
        while(cur)
        {
            while(cur&&cur->val==lt->val)
            {
                lt->next=cur->next;
                cur=cur->next;
            }
            
            lt=cur;
            if(cur)
                cur=cur->next;
        }
        
        return head;
    }
};