Question

I want to reference the 1st Dimension of a 2 Dimensional array using an enum. However, the configurations that each enum value represents sometimes overlap (not in any patterned way), meaning the data in the array will sometimes be the same. I therefore would like to have some elements point to the same array of data, as in the diagram below.

Is there any way of doing this at declaration-time in C++?

Answer 1

Yes, you can build an array like that using an array of pointers; you will be able to reference elements in that array as if it were a regular 2D array. Here is an example:

enum MyEnum {
    enumFirst = 0
,   enumSecond = 1
,   enumSecondShared = 2
,   enumThird = 3
};

static int enumFirstData[] = {1, 2, 3};
static int enumSecondData[] = {4, 3, 2};
static int enumThirdData[] = {9, 7, 8};

int *enumData[] = {
    enumFirstData
,   enumSecondData
,   enumSecondData // <== Shared
,   enumSecondData
};

Now you can reference elements of this array like this:

for (int i = 0 ; i != 3 ; i++) {
    cout << enumData[enumSecondShared][i] << endl;
}

Since you are using C++, using std::vector or std::array is a preferred way of making collections. You can use the same trick as above to establish shared collection elements.