LeetCode82. 删除排序链表中的重复元素 II（c++详解)

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        map<int,int>nums;
        ListNode *p = head;
        ListNode *new_head = new ListNode(0,head);
       
        ListNode *pre =  new_head;
        ListNode *temp = new_head;
        //new_head->next =head;
        while(p)
        {
            nums[p->val]++;
            p = p->next; 
        }
        pre = pre->next;
        while(pre){
            if(nums[pre->val] > 1){
                temp->next= NULL;
                pre =pre->next;
            }
            else {
             temp->next =pre;
             temp = temp -> next;
             pre = pre->next;
            }
            
        }
        
        if(temp == new_head) return NULL;
        return new_head->next;
        
    }
};

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        if (!head) {
            return head;
        }
        
        ListNode* dummy = new ListNode(0, head);

        ListNode* cur = dummy;
        while (cur->next && cur->next->next) {
            if (cur->next->val == cur->next->next->val) {
                int x = cur->next->val;
                while (cur->next && cur->next->val == x) {
                    cur->next = cur->next->next;
                }
            }
            else {
                cur = cur->next;
            }
        }

        return dummy->next;
    }
};