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Here is an implementation in C#. head of linked list is passed by ref because head may be deleted and so it may change.

public static void Delete(ref Node head, int data)
        {
            if (head != null)
            {
                Node curr = head;
                if (curr.data == data)
                    head = head.next;
                else
                {
                    while (curr.next != null)
                    {
                        if (curr.next.data == data)
                        {
                            curr.next = curr.next.next;
                            return;
                        }
                        curr = curr.next;
                    }
                }
            }
        }

public int deleteNode(LinkedListNode head, LinkedListNode n)
{
	      if( n == null) return -1;  
	      else
	      {
	    	   LinkedListNode current = head;
	    	   LinkedListNode previous = null;
                   while(current != null)
                   {
                       if(current.value == n.value)
                      {
                  //deletes first or middle elements, copy the node values from next node and deletes the //next node
                     if(current.next != null) 
                        {
                            current.value = current.next.value;
                            current.next = current.next.next;
                             return 0;
                         }
                         else
                         {
                            previous.next = null;
                            return 0;
                          }
                   }
                   //store the previous here just in case if the element to be deleted is the last node
                   previous = current; 
                   current = current.next; //move current to the next element
               }
	      }
	      return 1; 
}

public int deleteNode(LinkedListNode head, LinkedListNode n)
{
if( n == null) return -1;
else
{
LinkedListNode current = head;
LinkedListNode previous = null;
while(current != null)
{
if(current.value == n.value)
{
//deletes first or middle elements, copy the node values from next node and deletes the //next node
if(current.next != null)
{
current.value = current.next.value;
current.next = current.next.next;
return 0;
}
else
{
previous.next = null;
return 0;
}
}
//store the previous here just in case if the element to be deleted is the last node
previous = current;
current = current.next; //move current to the next element
}
}
return 1;
}

when there is only 1 element
previous is null
you cannot access previous

previous.next = null is an error

else
{
previous.next = null;
return 0;
}