Remove Linked List Elements

Problem

Given the head of a linked list and an integer val, remove all the nodes of the linked list that has Node.val == val, and return the new head.

Constraints

• The number of nodes in the list is in the range [0, 104].
• 1 <= Node.val <= 50
• 0 <= val <= 50

Solution

The problem Remove Linked List Elements can be solved by adding a dummy head to the beginning of the given head and removing nodes that has Node.val == val.

Implementation

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

        while (node->next != NULL)
        {
            if (node->next->val == val)
                node->next = node->next->next;
            else
                node = node->next;
        }

        return head->next;
    }
};