Looping in a spiral

Question

A friend was in need of an algorithm that would let him loop through the elements of an NxM matrix (N and M are odd). I came up with a solution, but I wanted to see if my fe

Answer 1

Just for fun in Javascript:

function spiral(x, y) {
  var iy = ix = 0
    , hr = (x - 1) / 2
    , vr = (y - 1) / 2
    , tt = x * y
    , matrix = []
    , step = 1
    , dx = 1
    , dy = 0;

  while(matrix.length < tt) {

    if((ix <= hr && ix >= (hr * -1)) && (iy <= vr && (iy >= (vr * -1)))) {
      console.log(ix, iy);
      matrix.push([ix, iy]);
    }

    ix += dx;
    iy += dy;

    // check direction
    if(dx !== 0) {
      // increase step
      if(ix === step && iy === (step * -1)) step++;

      // horizontal range reached
      if(ix === step || (ix === step * -1)) {
        dy = (ix === iy)? (dx * -1) : dx;
        dx = 0;  
      }
    } else {
      // vertical range reached
      if(iy === step || (iy === step * -1)) {
        dx = (ix === iy)? (dy * -1) : dy;
        dy = 0;
      }
    }
  }

  return matrix;
}

var sp = spiral(5, 3);