LEEDCODE 203移除链表元素

/**
 * 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* removeElements(ListNode* head, int val) {
        if(head == nullptr)
        {
            return nullptr;
        }
        ListNode* _dummyhead = new ListNode(0);
        _dummyhead->next = head;

        ListNode* pre = _dummyhead;
        ListNode* cur = _dummyhead->next;
        while(cur)
        {
            if(cur->val == val)
            {
                ListNode* p = cur;
                pre->next = cur->next;
                cur = cur->next;
                delete p;

            }
            else
            {
                cur = cur->next;
                pre = pre->next;

            }
        }
        return _dummyhead->next;

        
    }
};