Splitting a linked list into two lists

[fg350]

Hi everyone. So I wrote a function that adds a set of XYZ coordinates to a linked list, and that all worked fine. But now I'm trying to figure out how to take that list and split it into two lists at a given number. I CANNOT FOR THE LIFE OF ME FIGURE OUT HOW TO DO THIS. Here is my code for the list of coordinates: (List of numbers comes out like "66 12 234 3 20 88 4 5 6."

I literally have no idea where to even start, so if someone could explain and push me in the right direction that would be great. I assume I have to have a splitList function that has two pointers that point to NULL? And then after that I have no idea.

  class XYZ
{
private:
    double x;
    double y;
    double z;
    XYZ* next;
    
public:
    
    void report()
    {
        cout <<x <<" " <<y <<" " <<z << " " ;
    }
    
    // all coordinates have to be at least +1; Constructor to initialize node
    XYZ( double x1, double y1, double z1 )
    {
        x = pushup(x1);
        y = pushup(y1);
        z = pushup(z1);
        next = NULL;
    }
    
    // returns number at least +1
    double pushup( double x )
    {
        if( x<1) { x = 1; }
        return x;
    }
    
    // access
    void setNext( XYZ *p  ) { next = p; } // mutator: sets the value of Next
    XYZ* getNext() { return next; } // accessor
};


// prototype
void addXYZ( double, double, double, XYZ*&);
void report( XYZ*);

int main () {
    
    XYZ *coordList;  // head of the list
    coordList = NULL; // pointer is initialized as empty
    
    addXYZ( 4 , 5 , 6, coordList );
    addXYZ( 3 , 20 , 88, coordList );
    addXYZ( 66 , 12 , 234, coordList );
    
    report( coordList );
    
    return 0;
}


// function to add an XYZ to the list
void addXYZ( double x, double y, double z, XYZ* &head )
{
    XYZ* pCoord = new XYZ( x, y, z );
    pCoord->setNext( head ); //pCoord->next = coordList;
    head = pCoord;
    
}

// takes a list of XYZ objects and reports their values
void report( XYZ* head )
{
    XYZ* current = head;
    while ( current != NULL )
    {
        current->report(); // report the number at that node
        current = current->getNext(); // move on to next node to report until it reaches the end (NULL)
    }
}

[keskiverto]

What would this do:

void foo( XYZ* lhs, XYZ* & rhs ) {
  if ( lhs ) {
    auto bar = lhs->getNext();
    lhs->setNext( nullptr );

    if ( bar ) {
      if ( ! rhs ) rhs = bar;
      else {
        auto tail = rhs;
        while ( tail->getNext() ) tail = tail->getNext();
        tail->setNetx( bar );
      }
    }
  }
}

[fg350]

keskiverto,

Could you explain your code? I really don't understand what any of that means

[keskiverto]

"any of that"? Seriously?

Surely you do understand line 1, the getNext(), setNext(), if, else, while?

By syntax the lhs, rhs, bar, and tail are names (of variables), are they?

C++11 introduced nullptr to replace the less specific NULL.
C++11 gave auto a new meaning. Both here effectively evaluate to XYZ*.