remove-linked-list-elements.cpp

/**
 * 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) {
     
        auto dummy = new ListNode(-1, head), pre = dummy, cur = head;
        while (cur) {
            if (cur->val == val)  pre->next = cur->next;
            else pre = cur;
            
            cur = cur->next;
        }
        return dummy->next;
    }
};