Rotate a Matrix by +180 degrees.

RotateMatrixByOneEightyDegree

package com.interview.coding.crack;

public class RotateMatrixByOneEightyDegree {

	public void rotateByOneEightyDegree(int[][] array, int m, int n)
	{
		for(int i = 0; i < ((m/2) + (m%2)); i++)
		{
			int first = i;
			int last = n - 1;
			for(int j = 0; j < n; j++)
			{
				int offset = last - i; 
				int top = array[first][j];
				array[first][j] = array[offset][last - j];
				array[offset][last - j] = top;
			}
		}
	}
	
	public void printArray(int[][] array, int m, int n)
	{
		for(int i = 0; i < m; i++)
		{
			for(int j = 0; j < n; j++)
			{
				System.out.print(array[i][j] + "\t");
			}
			System.out.println();
		}
		System.out.println("|--------------------------------------|");
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		RotateMatrixByOneEightyDegree rotateBy180 = new RotateMatrixByOneEightyDegree();
		int two[][] = new int[][]{{1,2}, {3,4}};
		int three[][] = new int[][]{{1,2,3}, {4,5,6}, {7,8,9}};
		int four[][] = new int[][]{{1,2,3,4}, {5,6,7,8}, {9,10,11,12}, {13,14,15,16}};
		int five[][] = new int[][]{{1,2,3,4,5}, {6,7,8,9,10}, {11,12,13,14,15}, {16,17,18,19,20}, {21,22,23,24,25}};
		int six[][] = new int[][]{{1,2,3,4,5,6}, {7,8,9,10,11,12}, {13,14,15,16,17,18}, {19,20,21,22,23,24}, {25,26,27,28,29,30}, {31,32,33,34,35,36}};
		
		System.out.println("2x2 Array");
		rotateBy180.printArray(two, 2, 2);
		System.out.println("2x2 Array - 180*degree");
		rotateBy180.rotateByOneEightyDegree(two, 2, 2);
		rotateBy180.printArray(two, 2, 2);
		System.out.println();
		
		System.out.println("3x3 Array");
		rotateBy180.printArray(three, 3, 3);
		System.out.println("3x3 Array - 180*degree");
		rotateBy180.rotateByOneEightyDegree(three, 3, 3);
		rotateBy180.printArray(three, 3, 3);
		System.out.println();
		
		System.out.println("4x4 Array");
		rotateBy180.printArray(four, 4, 4);
		System.out.println("4x4 Array - 180*degree");
		rotateBy180.rotateByOneEightyDegree(four, 4, 4);
		rotateBy180.printArray(four, 4, 4);
		System.out.println();
		
		System.out.println("5x5 Array");
		rotateBy180.printArray(five, 5, 5);
		System.out.println("5x5 Array - 180*degree");
		rotateBy180.rotateByOneEightyDegree(five, 5, 5);
		rotateBy180.printArray(five, 5, 5);
		System.out.println();
		
		System.out.println("6x6 Array");
		rotateBy180.printArray(six, 6, 6);
		System.out.println("6x6 Array - 180*degree");
		rotateBy180.rotateByOneEightyDegree(six, 6, 6);
		rotateBy180.printArray(six, 6, 6);
		System.out.println();
	}

}

public void rotateByOneEightyDegree(int[][] array, int m, int n)
{
    int lastM = m-1;
    int temp;
    for(int i = 0; i <= m/2; i++)
    {
        int lastN = n-1;
        for(int j = 0; j < n; j++, lastN--)
        {
            if(i == lastM && j >= lastN) {
                break;
            }else {
                //swap
                temp = array[i][j];
                array[i][j] = array[lastM][lastN];
                array[lastM][lastN] = temp;
            }
        }
        lastM--;
    }
}

This is what I actually imagined when I told you the answer.

Yes, this is exactly the break I was telling you about :)