On the C# variant you have an error in line 83 that prevents code to be evaluated. PrintSinglyLinkedList(llist->head, "\n", textWriter); I think it should be: PrintSinglyLinkedList(llist_head, "\n", textWriter); Not all the time java code works in C# :D

Java Solution we want to insert the node head of the sll(sll Node,int data) { sll new head= new sllNode(data); if(list!=NULL) { Node.next=list return new head }

Java Solution we want to insert the node head of the sll(sll Node,int data) { sll new head= new sllNode(data); if(list!=NULL) { Node.next=list return new head }

My Java solution with o(1) time complexity and o(1) space complexity:

static SinglyLinkedListNode insertNodeAtHead(SinglyLinkedListNode llist, int data) {
        SinglyLinkedListNode newHead = new SinglyLinkedListNode(data);
        newHead.next = llist;
        return newHead;
    }

python 3

def insertNodeAtHead(llist, data):
    new_node = SinglyLinkedListNode(node_data=data)
    if llist is None:
        return new_node
    else:
        new_node.next = llist
        return new_node