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.

C++ Solution:

/**

  * 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) {

         ListNode* current = head;

         ListNode* p;

         while(current!=NULL && current->next != NULL) {

             if (current->val == current->next->val) {

                 p = current->next;

                 current->next = p->next;

                 free(p);

                
             }

             else {

                 current= current->next;

             }

         }

        
         return head;

     }

};