2181. Merge Nodes in Between Zeros

You are given the head of a linked list, which contains a series of integers separated by 0’s. The beginning and end of the linked list will have Node.val == 0.

For every two consecutive 0’s, merge all the nodes lying in between them into a single node whose value is the sum of all the merged nodes. The modified list should not contain any 0’s.

Return the head of the modified linked list.

/**
 * 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* mergeNodes(ListNode* head) {
        ListNode* cur = head;
        while(cur->next) {
            if(cur->next->val == 0) {
                if(cur->next->next) {
                    cur = cur->next;
                } else {
                    cur->next = NULL;
                }
            } else {
                cur->val += cur->next->val;
                cur->next = cur->next->next;
            }
        }
        return head;
    }
};