2807. Insert Greatest Common Divisors in Linked List .cpp leetcode

/**
 * 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* insertGreatestCommonDivisors(ListNode* head) {
        auto head_copy = head;
        while(head!= nullptr && head->next!=nullptr){
            int gcd = __gcd(head->val,head->next->val);
            auto curr_next = head->next;
            head->next = new ListNode(gcd,curr_next);
            head = head->next->next;
        }
        head = head_copy;
        return head;
    }
};