Array with loop for incrementation

Projects General Guidance
1

Hi Everyone,
I'm new with Arduino and trying to get to use arduino to control xmas led strips.
I've made a snowflake that I want to animate. Therefore, I've created arrays for the different parts of an arm of the snowflake.

int innerstar[8] = {2, 4, 1, 3, 30, 27, 29, 28};
int outterstar[12] = {9, 10, 8, 11, 7, 12, 24, 19, 23, 20, 22, 21};
int branch[10] = {5, 6, 13, 14, 15, 16, 17, 18, 25, 26};

My problem is the following. Instead of creating 6 arrays for each part, or one array with 6 times as many leds, is it possible to increment the numbers of the arrays ?
I've tried this (not optimized yet), but it doesn't work anyway.

for (int i = 0; i <= 8; i++) {
    leds[[innerstar[i]] = CRGB (0, 0, 255);
    leds[[innerstar[i]+30] = CRGB (0, 0, 255);
    leds[[innerstar[i]+60] = CRGB (0, 0, 255);

    FastLED.show();
}

Is it possible to increment the numbers of the arrays this way ?
Thank you for your help.

2

Yes. The name for such an array is called a "two dimensional " array.

leds[1][innerstar[i]] = CRGB (0, 0, 255);
3

Thank you. 2D arrays work great. I do have one more question, though. What is best between using a 2D array such as

int array[6][12] = {{ val1, val2, ... val12}, {val1+10, val2+10,...},... {val1+50, val2+50...}...}
for (int x= 0; x<6; x++
for (int y=0; x<12; y++
leds[array[x][y]] = CRGB (0, 0, 255)

or using a simple array combined with a loop such as

int array[12] = { val1, val2, ... val12};
for (int z = 0; z<60; z=z+10)
for (int i=0; i<12; i++)
leds[array[i]+z] = CRGB (0, 0, 255)

I guess one is better than the other ?

4

The second solution uses less memory.
It is clearer if you properly align your code.
Curly braces are missing as well.
It may also be clearer to have the z loop as inner loop.

5

Thnak you so much for your answers.
Yes, I wrote the line poorly only to give an idea of the two solutions. I'll go for the memory savings, then. As well to get the good habits from the start.
Thanks again

6

I agree.

In this case I'd like to know just how much memory is saved, at the possible cost of complicating or obscuring your algorithm(s), which may make more sense when you are reading as 2D x and y.

If you find yourself converting an index into its constituent row/column values or vice versa, or otherwise bending over backwards to save something, make sure that doing is worth it in the long run.

a7