[leetcode]-82. Remove Duplicates from Sorted List II（C语言）

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

Example 1:

Input: 1->2->3->3->4->4->5
Output: 1->2->5

Example 2:

Input: 1->1->1->2->3
Output: 2->3

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* deleteDuplicates(struct ListNode* head) {
    if(head==NULL||head->next==NULL)
        return head;
    struct ListNode *p;
    p=(struct ListNode *)malloc(sizeof(struct ListNode));
    p->next=head;
    head=p;
    int a;
    while(head->next!=NULL&&head->next->next!=NULL)
    {
        if(head->next->val==head->next->next->val)
        {
            a=head->next->val;
            while(head->next!=NULL&&head->next->val==a)
                head->next=head->next->next;
        }
        else
            head=head->next;
    }
    return p->next;
}