Problem 2816

function doubleIt(head: ListNode | null): ListNode | null {
    if(head === null) {
        return head;
    }
    const root = new ListNode(1, head);
    const noMore = head.val < 5; 
    
    while(head.next !== null) {
        head.val = (head.val * 2) % 10;
        if(head.next.val * 2 > 9) {
            head.val++;
        }
        head = head.next;
    }
    head.val = (head.val * 2) % 10;
        
    return noMore ? root.next : root;
};