/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */
/**
 * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
 *
 * 
 * @param head ListNode类 
 * @return ListNode类
 */
struct ListNode* deleteDuplicates(struct ListNode* head ) {
    // write code here
    if(head==NULL){
        return NULL;
    }
    struct ListNode*pre=head;
    while(pre->next&&pre){
        if(pre->val==pre->next->val){
            struct ListNode*tmp=pre->next;
            pre->next=tmp->next;
            free(tmp);
        }
        else{
            pre=pre->next;
        }
    }
    return head;
}