There are problems with the C# compilation. I suppose the NULLABLE setting should be disabled in project file. And the problem is not only with this task.

Compilation error :(

Check the compiler output, fix the error and try again.

Compile Message

/tmp/submission/20231128/08/54/hackerrank-13c0afafe2e3cf5fd37ee00b3e5a9f6b/code/Solution.cs(32,25): warning CS8625: Cannot convert null literal to non-nullable reference type. [/tmp/submission/20231128/08/54/hackerrank-13c0afafe2e3cf5fd37ee00b3e5a9f6b/code/Solution.csproj]

Here C# solution have some issue. Same code base from python, is working fine.

Python

def insertNodeAtHead(llist, data):
    # Write your code here
    head =  SinglyLinkedListNode (data)
    head.next = llist
    return head

C#

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

Amazing stuff, could you please let us know how to execute this code. i need it to run for my law site awaiting for your kind response.

C# code submission always fails as it has -> operator.

/tmp/submission/20231026/22/16/hackerrank-4ca2478418d197f5b158d12e97aa4e5d/code/Solution.cs(85,31): error CS0193: The * or -> operator must be applied to a pointer [/tmp/submission/20231026/22/16/hackerrank-4ca2478418d197f5b158d12e97aa4e5d/code/Solution.csproj]

Here's a Python 3 code with O(1) time Complexity (Correct me if I'm wrong):

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