Leetcode: Remove Duplicates from Sorted List

http://oj.leetcode.com/problems/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) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if(head==NULL) return head;
        while(head->next!=NULL&&head->val==head->next->val){
            head->next=head->next->next;
        }
        deleteDuplicates(head->next);
        return head;
    }
};