Thanks!

I know another one problem that can be solved using 3D BIT (100246B - Звёзды), but its statement only available in russian. But i can try to translate it.

You are given a cube (coordinates of points in a cube is 0-indexed) with a side n (1 ≤ n ≤ 128) and 2 types of queries. Each query starts with its type (1 or 2). Type 1 is followed by 4 integers x, y, z, k (x, y, z — coordinates, k ( - 2·10⁴ ≤ k ≤ 2·10⁴) — the number of appeared/lost stars in this point (i don't know that i wrote it understandable) (i.e. that query means such operation: cube[x][y][z] +  = k). Type 2 query is followed by 6 integers x1, y1, z1, x2, y2, z2 — coordinates of subcube, you have to count number of stars in it (i.e. for x in[x1; x2]: for y in[y1; y2]: for z in[z1; z2]: res +  = cube[x][y][z]).

I was reading 2D BIT, gfg implementation https://www.geeksforgeeks.org/two-dimensional-binary-indexed-tree-or-fenwick-tree/

Please help me with some doubts, In the updateBit and getSum function inner "y" loop is not initialized again. Is it a mistake or is it meant to be that way?

If it is meant to be that way can you explain how is it working and what is the need of outer loop as the same work can be done with the help of an "if" statement.

Thanks in advance..

Is the English version of this book available?