Square arrays from non-square numbers

//  PROBLEM
//  so I've run into this at least twice now, where I want to loop through a single 
//  "0 to whatever" range of numbers, but within that loop use the current iteration to 
//  address a 2D array.
//
//  this is in Processing, so the actual use case is creating a 2D grid of coordinates
//  from that single range of numbers. Usually I do it with two loops, ie. loop
//  through i and then loop through j within that loop. But I'm finding cases where
//  I want to loop through just i, and derive separate X and Y coordinates from the 
//  current value of i. Easy to do if i is a square, but what if it's irregular?
//
//  I'm not sure if I'm explaining it very well, but here's what I came up with. I thought
//  it was a neat bit of math. Code in Processing / Java.


int count = 1337;

for (int i = 0; i < count; i++) {

  float sqc = sqrt(count);

  X = (sqc - ((count - (i + 1)) % sqc));
  Y = ceil(sqc - (sqc - (i + 1) / sqc));

}

It's for aligning coordinates in a grid. Say I want to set up a variable number of squares without having to worry about them matching up perfectly. Done.