Container class with 1D array

[XboxOne2019]

Hey guys, we are supposed to be doing this program using a container class to store (x, y) values in and I already wrote this program using a 2D array, but did not turn it in. Others used the 2D array as well and our professor commented that that was "interesting". Guess we were not supposed to use a 2D. My question is, how to do this with a 1D array because you have two separate member functions called getXElement() and getYElement()?

Also we have not learned vectors and cannot call std library stuff other than basic knowledge

He showed us the idea of the array like this:
[xy], [xy], [xy] but how would the array know you are calling an individual x or y.

Instructions:
You are to implement a 'List' class to handle a list with general operations. That means you can insert and delete any element anywhere in the list. Your list will be an array. Your general list will store X Y coordinates, i.e. pairs of numbers in the array. The list has no order, except for the order you insert or delete. The methods you are to implement are as given:

Constructor methods (two, default and copy constructor, a list to a newly defined list, ie 'List listA(listB)' )

empty returns true or false if list is empty or not.

first makes current position at the beginning of the list

last makes current position at the end of a list.

prev places current position at the previous element in the list

next places current position at the next element in the list

getPos returns current position or where you are in the list

setPos(int) places current position in a certain position in the list

insertBefore(int,int) inserts a new element before the current position

insertAfter(int, int) inserts a new element after the current position

get X Element returns the one element that current position is pointing to

get Y Element returns the one element that current position is pointing to

size returns the size of the list (number of elements in list)

replace(int,int) replace the current element with a new value X Y value

erase deletes the current element

clear makes the list an empty list

overload the operators: (at least) << output, ==, !=, + ,+=, { = (assignment) maybe? }

You are to implement the List class using an array. For now the array can be 20 in size.

You will need to use the 'ElementType' for 'typing' your data.

You will need to use CAPACITY constant for the size of the array, in case we need to change the array size.

Invariants: The elements in the list are to be left justified with in the array. ‘pos’ will point to a valid location in the array (ie where data is located. On insert, ‘pos’ should point to the element just inserted on insert operations. ‘pos’ should never be outside of element list.


main program to be used with the class:

int main()
{
    
   List a, b; 
   int endit;

//inserting values in list a 
for (int i=1;i<=10;i++)
{
    a.insertAfter(i, i * 2);
}

//printing list a 
cout << "List a : " << endl;
cout << " " << a << endl;
cout << "Number of elements in a - " <<a.size()<<endl;

//inserting values in list b 
for (int i=1;i<=10;i++)
{
   b.insertBefore(i, i * 2); 
}

//printing list b 
cout << "List b : " << endl;
cout << " " << b << endl;
cout << "Number of elements in b - " <<b.size()<<endl;

//comparing list a and list b 
if (a == b)
{
    cout << "a == b: List a & b are equal" << endl;
}

else
{
    cout << "a == b: List a & b are NOT equal" << endl;
}


//finding the first element in each list 
a.first();
b.first();
cout<<"First element in list a: (" << a.getXElement() << "," << a.getYElement()<<")" <<endl;
cout<<"First element in List b: (" << b.getXElement() << "," << b.getYElement()<<")" <<endl;

//finding the last element in each list 
a.last();
b.last();
cout << "Last element in list a: (" <<a.getXElement() << "," << a.getYElement()<<")" <<endl;
cout << "Last element in list b: (" <<b.getXElement() << "," << b.getYElement()<<")" <<endl;

cout << endl << endl << " Start of new stuff" << endl;

//erasing list b 
b.clear();
cout << "b.erase(): Empty List b: " << b << endl;

//comparing list a and b again as not equal
if (a != b)
{
    cout << "a != b: List a & b are not equal" << endl;
}

else
{
    cout << "a != b: List a & b are equal" << endl;
}


//inserting new values into list b
for (int i=1;i<=10;i++)
{
    b.insertBefore(i, -i*2);
}

 cout << "List b with neg y's" << endl;
 cout<< "List b: "<< b <<endl;

//performing more calculations 
a.setPos(5);
b.first();
for (int i=1;i<8;i++)
{
  a.erase();
  b.replace(i, i*3);
  b.next();
}

cout << "Modified Object 'a' (erase 3) " << endl;
cout << "List a: " << a << endl;
cout << "Modified Object 'b' (replace 3)" << endl;
cout << "List b: " << b << endl;

//copying list b into c 
List c(b);
cout << "Copy Constructor c(b)" << endl;
cout << "List b : " << b << endl;
cout << "List c : " << c << endl;


//comparing c and b 
if (c == b)
cout << "List c & b are equal" << endl;
else
cout << "List c & b are Not equal" << endl;

//list c and e 
List e;
e = c;
cout << "Object 'c' assigned to Object 'e':" << endl;
cout << "List c : " << c << endl;
cout << "List e : " << e << endl;

List d;
d = a;

d.first();
endit = d.size()/2;
for (int i = 1; i < endit; d.next(), i++)
{
    d.insertBefore(d.getXElement()*2, d.getYElement()*2);
    d.next();
}
cout << "Results after some inserts at front of d " << endl;
cout << "List d : " << d << endl;

a.first();
endit = a.size();
for (int i = 1; i < endit; a.next(), i++)
{
   a.replace(a.getPos()-a.getXElement(), a.getPos()-a.getYElement());
   a.next();
}
cout << "Results after adding pos & flipping signs on list a" << endl;
cout << "List a : " << a << endl;

List alist(b);
alist.clear();
for (int i=1;i<=5;i++)
alist.insertAfter(i, i-1);
alist.first();

cout << "New List alist with positions above: " << endl;

for (int i=1;i<=5;i++) 
{
   cout << setw(8) << alist.getPos();
   alist.next();
}
cout << endl;
alist.first();

for (int i=1;i<=5;i++) 
{
  cout << setw(6) << alist.getXElement() << "," << alist.getYElement();
  alist.next();
}
cout << endl;

cout << endl << " check out boundary conditions" << endl;
List sq;
cout << "number of elements in empty sq list = " << sq.size() << endl;
cout << " print empty list sq: " << sq << endl;
a.first();
sq.erase(); sq.erase();
cout << "First element in list a: (" << a.getXElement() << "," << a.getYElement()<<")"<< endl;
sq.setPos(5);
cout << "empty sq values " << sq << endl;
sq.insertBefore(333, 444);
cout << "sq list: " << sq << endl;
sq.next(); sq.next();
cout << "sq.getElement() = " << sq.getXElement() << "," << sq.getYElement() << endl;
cout << "sq list = " << sq << endl;
sq.prev(); sq.prev();
cout << "sq.getElement()= " << sq.getXElement() << "," << sq.getYElement() << endl;
cout<< "sq list = "<< sq << endl;

[jonnin]

there are a number of ways to do this.
you can roll your own:
struct xy {int x; int y;};
and container that up:
vector<xy> xypairs;
cout << xypairs[10].x; //just the x part of a 1d array of 2 things.

I show that because it scales to something bigger than 2 numbers. for simple data, you can also use std::pair, or tuple, etc instead of a home-rolled struct here.

you can use parallel arrays:
vector <int> xs; //all the x values.
vector <int> ys; //all the y values.
xs[10] is the x part of the 10th item.
ys[10] is the y part of the 10th item.

there are other exotic ways to do it that lapse into C or low level programming that gets ugly in a hurry. You don't want to do that kind of thing, but you 'can' for whatever that is worth, eg you can jack 2 32 bit ints into a single 64 bit int, or even 4 16s into one 64, as one horrible example of what not to do that is 'possible' :)

anyway, do those answer your question?
FYI: multiple dimensional arrays are a pain to pass in and out of functions. Vectors make this much nicer.

2d array was probably a fine solution given what you know so far. Its not wrong, you just didn't do what he expected. That should happen a lot, actually. If you always do what they expect, you are not being creative enough.