RotateMatrix.java

package array;

/**
 * Created by gouthamvidyapradhan on 21/03/2017.
 * You are given an n x n 2D matrix representing an image.

 Rotate the image by 90 degrees (clockwise).

 Follow up:
 Could you do this in-place?
 */
public class RotateMatrix
{
    /**
     * Main method
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception
    {
        int[][] A = {{1,2,3}, {4,5,6}, {7,8,9}};
        new RotateMatrix().rotate(A);
        for (int i = 0; i < A.length; i ++)
        {
            for(int j = 0; j < A[0].length; j ++)
            {
                System.out.println(A[i][j]);
            }
        }
    }

    public void rotate(int[][] matrix)
    {
        int lc = 0, tr = 0, rc = matrix[0].length - 1, br = matrix.length - 1;
        while(tr < br)
        {
            for(int i = lc, j = tr, k = rc, l = br; i < rc && j < br && k > lc && l > tr; i ++, j ++, k--, l--)
            {
                int temp1 = matrix[j][rc];
                matrix[j][rc] = matrix[tr][i];
                int temp2 = matrix[br][k];
                matrix[br][k] = temp1;
                temp1 = matrix[l][lc];
                matrix[l][lc] = temp2;
                matrix[tr][i] = temp1;
            }
            lc ++; tr ++; rc --; br --;
        }
    }
}