2d array rotation

Posted on 2011-03-23
Last Modified: 2012-05-11
how to rotate a 2d array (matrix) 90 degrees anticlockwise so:

X =
    1    2    3
    4    5    6
    7    8    9


Y =
    3    6    9
    2    5    8
    1    4    7
Question by:chudyksg
LVL 40

Expert Comment

Comment Utility
create another empty array of 3x3 dimension, and follow these steps

pick value at 1,1 and put it at 3,1
pick value at 1,2 and put it at 2,1
pick value at 1,3 and put it at 1,1
pick value at 2,1 and put it at 3,2
pick value at 2,3 and put it at 1,2
pick value at 3,1 and put it at 3,3
pick value at 3,2 and put it at 2,3
pick value at 3,3 and put it at 1,3
LVL 27

Accepted Solution

rrz earned 500 total points
Comment Utility
public int[][] rotateMatrixLeft(int[][] matrix)
    /* W and H are already swapped */
    int w = matrix.length;
    int h = matrix[0].length;   
    int[][] ret = new int[h][w];
    for (int i = 0; i < h; ++i) {
        for (int j = 0; j < w; ++j) {
            ret[i][j] = matrix[j][h - i - 1];
    return ret;

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Expert Comment

Comment Utility
This will rotate any matrix 90 degrees anti-clock.

* To rotate the array 90 degrees anti-clock wise. This will rotate square
* and non square matrix.
* @param sourceArray
* @return
public int[][] antiClock90Rotation(int[][] sourceArray) {
	int[][] rotatedArray = new int[sourceArray[0].length][sourceArray.length];
	int positionFactor = rotatedArray.length - 1;
	for (int i = 0; i < rotatedArray.length; i++) {
		for (int j = 0; j < rotatedArray[i].length; j++) {
			int a = i - positionFactor;
			a = (a < 0) ? -a : a;
			rotatedArray[i][j] = sourceArray[j][a];
	return rotatedArray;

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