🚀 go-pugleaf

I am trying to make a kind of linked list in c++. The linked list will
maintain sorted doubles. This would look something like this:

struct Node {
 double data;
 Node *next;
};

This is easy to do BUT in addition to this my linked list has to maintain
two orders: one taking sign into consideration and another that doesn't care
about the sign. So I think the data structure for this looks like this:

struct Node {
 double data;
 Node *nextSigned,*nextUnsigned;
};

I have successfully linked all the elements that take sign into account by
using an add function that appends the data in order. but how do i link the
unsigned parts together?

Example:
If the data was -2,5,3,-1
sorted list1: -2,-1,3,5  ---> I've done this successfuly
sorted list2: -1,-2,3,5  ---> HOW TO DO ThIS LIST?