Matrix rotation efficiency

Question

I am not sure if I should be using recursion or not or if it even helps in increasing the performance of my algorithm. I feel as though I am creating and replacing too many arrays by calling my inner rotate() function.

Should I add a check to convert rotation -270 to 90 and vice-versa so that I am rotating less often?

Please refer to the JSFiddle I have provided for details and clarification on the functions involved in the code below: JSFiddle Demo

var rotateMatrix = function (matrix, n, direction) {
 var ret = matrix.slice();
 var rotate = function(direction, matrix) {
 var r = zeroArr(n, n);
 for (var i = 0; i < n; i++) {
 for (var j = 0; j < n; j++) {
 if (direction < 0) {
 r[i][j] = matrix[n - j - 1][i];
 } else {
 r[i][j] = matrix[j][n - i - 1];
 }
 }
 }
 return r;
 };
 for (var turn = Math.abs(direction); turn > 0; turn -= 90) {
 ret = rotate(direction, ret);
 }
 return ret;
};
var tile = [
 ['A', 'B', 'C'],
 ['D', 'E', 'F'],
 ['G', 'H', 'I']
];
trace2('Rotate +180', printMatrix(rotateMatrix(tile, 3, 180)));
trace2('Rotate +90', printMatrix(rotateMatrix(tile, 3, 90)));
trace2('Orginal', printMatrix(tile));
trace2('Rotate -90', printMatrix(rotateMatrix(tile, 3, -90)));
trace2('Rotate -180', printMatrix(rotateMatrix(tile, 3, -180)));

Output:

Rotate +180:
 I| H| G
--+--+--
 F| E| D
--+--+--
 C| B| A
Rotate +90:
 C| F| I
--+--+--
 B| E| H
--+--+--
 A| D| G
Orginal:
 A| B| C
--+--+--
 D| E| F
--+--+--
 G| H| I
Rotate -90:
 G| D| A
--+--+--
 H| E| B
--+--+--
 I| F| C
Rotate -180:
 I| H| G
--+--+--
 F| E| D
--+--+--
 C| B| A

Answer 1

The n parameter is redundant, as it should be possible to deduce the matrix dimensions from matrix itself, using matrix.length and matrix[0].length. You seem to have made the assumption that matrix is square — you should either document or relax the restriction.

I suggest writing three separate inner functions for the three possible rotations. One code-reuse technique you could use for the ±90° rotations is to combine transpose and row-swap operations.

• Mr. Polywhirl: Wow, that question was insightful. I have come up with the ollowing: Updated JSFiddle. Should I append these changes to my question for others to view? Is there any other way to optimize this?
• Vogel612: @Mr.Polywhirl Concerning changes to reviewed code, you might want to read this meta-post