I'm trying to find a formula for

copy[3] = b.data[0]
copy[4] = b.data[1]
copy[5] = b.data[2]
copy[9] = b.data[3]
copy[10] = b.data[4]
copy[11] = b.data[5]

letting the right hand side be b.data, I can see this is like

copy[3] = b.data[0] multiply by 2, add 3
copy[4] = b.data[1] multiply by 2, add 2
copy[5] = b.data[2] multiply by 2, add 1
copy[9] = b.data[3] multiply by 2, add 3
copy[10] = b.data[4] multiply by 2, add 2
copy[11] = b.data[5] multiply by 2, add 1

there's obviously a modulo pattern going on so I've tried

copy[i*2 + (rows +(-1*i) % (rows + 1))] = b.data_;

(rows = 3)

which gives me the adding pattern 3 2 1 0 3 2 1 0

however I need to miss out the 0, can anyone see how to do this?

Thanks in advance!

To go from the right hand side index to the left handside index the maths computationally is as follows

int cycle_rhs(3), cycle_rhs(6);
int temp =  x/cycle_rhs; //this gives a floor so no remainder
int temp2 = cycle_lhs * temp;
/*
0 , 1, 2 ->0
3, 4, 5 -> 6
*/
int offset_lhs(3);

y = temp2 + offset_lhs + x%cycle_rhs;

I note though that you are doing a matrix mthod why
not have a

std::vector<int> get_column(int id);
bool resize_matrix(int width, int height, int value = 0);
bool set_column(std::vector<int> &vals);

set of methods

I'm trying to find a formula for

copy[3] = b.data[0]
copy[4] = b.data[1]
copy[5] = b.data[2]
copy[9] = b.data[3]
copy[10] = b.data[4]
copy[11] = b.data[5]

letting the right hand side be b.data, I can see this is like

copy[3] = b.data[0] multiply by 2, add 3
copy[4] = b.data[1] multiply by 2, add 2
copy[5] = b.data[2] multiply by 2, add 1
copy[9] = b.data[3] multiply by 2, add 3
copy[10] = b.data[4] multiply by 2, add 2
copy[11] = b.data[5] multiply by 2, add 1

there's obviously a modulo pattern going on so I've tried

copy[i*2 + (rows +(-1*i) % (rows + 1))] = b.data_;

(rows = 3)

which gives me the adding pattern 3 2 1 0 3 2 1 0

however I need to miss out the 0, can anyone see how to do this?

Thanks in advance!

Thanks for the reply tetron but I didn't really understand your method...

EDIT - solved it another way.