Description

Submission

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* removeElements(ListNode* head, int val) {
        ListNode* prevNode = head;

        for(ListNode* node = head; node;) {
            if(node->val == val) {
                if(head == node) {
                    head = node = head->next;
                } else {
                    prevNode->next = node = node->next;
                }
            } else {
                prevNode = node;
                node = node->next;
            }
        }
        return head;
    }
};

Submission 210605

/**
 * 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) {
        ListNode* dummy = new ListNode(-1, head);

        ListNode* prev = dummy;
        for(ListNode* ptr = dummy->next; ptr; ptr = ptr->next) {
            if(ptr->val == val) {
                prev->next = ptr->next;
            } else {
                prev = ptr;
            }
        }

        return dummy->next;
    }
};