LeetCode 82. 删除排序链表中的重复元素 II

82. 删除排序链表中的重复元素 II

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        unordered_map<int,int> mp;
        ListNode* cur = head;
        while(cur){
            mp[cur->val]++;
            cur = cur->next;
        }
        ListNode* dump = new ListNode();
        dump->next = head;
        ListNode *pre = dump;
        cur = head;
        while(cur){
            if(mp[cur->val]>1){
                pre->next = cur->next;
            }else{  
                pre = cur;
            }
            cur = cur->next;
        }
        return dump->next;
    }
};

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        ListNode* dump = new ListNode;
        dump->next = head;
        ListNode* cur = head, *pre = dump;

        while(cur){
            if(cur->next && cur->val == cur->next->val){
                int val = cur->val;
                while(cur && cur->val == val){
                    cur = cur->next;
                }
                pre->next = cur;
            }else{
                pre = cur;
                cur = cur->next;
            }
        }
        return dump->next;
    }
};