# Matrix rotation efficiency

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


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