Question

Let’s say if I have a row with 3+ attributes A, B, C and other Attrs

row1: A=1, B=5, C=10, Other Attrs
row2: A=1, B=5, C=10, Other Attrs
row3: A=2, B=5, C=10, Other Attrs
row4: A=2, B=5, C=10, Other Attrs
row5: A=3, B=6, C=11, Other Attrs
row6: A=3, B=6, C=11, Other Attrs

So if I want to assign each row a group ID by combination of A, B, C, row1, row2 have same group id x, row 3 row 4 have group id y, row 5 row 6 have group id z.

A simple solution is:

group id = A * S + B * S^2 + C * S^3 (S is the max integer number)

But my problem is I need an algorithm to back out each of A, B, C value from group id

for example, I need to be able to back out A=1, B=5, C=10 from group id x solely

Answer 1

First, this would be enough:

group id = A + B * S + C * S^2;

To get back A, B, and C:

A = id % S;

B = (id / S) % S;

C = (id / S^2);

Where / is integer division and % is modulo.