Final answer:
To start a class declaration for a node in a linked list with double data, define a class with a double type member variable and a pointer to the next node, initializing the pointer to nullptr in the constructor.
Step-by-step explanation:
To declare the start of a class for a node in a linked list where the data is of type double, you would define the class with a member variable to hold the double value and a pointer to the next node. Here is a simple example in C++:
class ListNode {
public:
double data;
ListNode* next;
// Constructor
ListNode(double val) : data(val), next(nullptr) {}
};
The ListNode class has a public member variable named 'data' that stores a double value. It also has a pointer to the next ListNode, which is initialized to nullptr in the constructor. This forms the basis for a singly linked list.