82&83 删除排序链表中的重复元素

/**
 * 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 *pre, *current,*head_res;
        current = head;
        if(current==NULL||current->next==NULL)
        return current;
        head_res = new ListNode;
        head_res->next = head;
        pre = head_res;
      int del_val;
        while(current&&current->next)
        {
            if(current->val == current->next->val)
            {
                del_val = current->val;//del_val = 3 del_val = 4
                while(current&&current->val==del_val)
                {
                    pre->next = current->next; //2->3 2->4 2->5
                    current = current->next; //current = 3 current = 4 current = 5
                }
            }
            else
            {
                pre->next = current;//0->1 1->2
                current = current->next;//current = 2 current = 3
                pre = pre->next;//pre = 1 pre = 2
            }
            


        }
        return head_res->next;
        delete(head_res);
        
    }
};