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 *start = head;        ListNode *end = head->next;                while (start!=NULL) {            while (end!=NULL && start->val==end->val) {                end = end->next;            }                        start->next = end;                        start = start->next;            end = start;        }        return head;    }};

这里是否应该考虑那些被删除的节点的内存释放问题？