(leetcode)删除链表中的重复元素

给定一个排序链表，删除所有含有重复数字的节点，只保留原始链表中 没有重复出现 的数字

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */

typedef struct ListNode node;
struct ListNode* deleteDuplicates(struct ListNode* head){
       struct ListNode* dummyHead = (node* )malloc(sizeof(node));
       dummyHead->next = head; 
       struct ListNode* pre = dummyHead;
       struct ListNode* cur;
       struct ListNode* difNode;
       cur = difNode = head;
       int curRepeatnum = 0;
       
       while(cur){
             if(difNode&&difNode->val==cur->val){
                 ++curRepeatnum;
                 difNode = difNode->next;
             }else{ 
                 if(curRepeatnum > 1){
                     pre->next = difNode;
                     cur = difNode;
                 }else{
                     cur = difNode;
                     pre = pre->next;
                 }
                 curRepeatnum = 0;
             }
       }
       return dummyHead->next;
}