# 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[0].length. You seem to have made the assumption that matrix is square — you should either document or relax the restriction.