Lecture Notes on 24 Jul 2013

public class Array
{
  public static int[][] matrixMultiply (int[][] a, int[][] b)
  {
    int[][] c = new int [a.length][b[0].length];
    for (int i = 0; i < a.length; i++)
    {
      for (int j = 0; j < b[0].length; j++)
      {
        int sum = 0;
	for (int k = 0; k < a[0].length; k++)
	{
          sum += a[i][k] * b[k][j];
	}
	c[i][j] = sum;
      }
    }

    return c;
  }

  public static int[][] transpose (int[][] a)
  {
    int[][]b = new int [a[0].length][a.length];
    for (int i = 0; i < a.length; i++)
    {
      for (int j = 0; j < a[i].length; j++)
      {
        b[j][i] = a[i][j];
      }
    }
    return b;

  }

  public static int[][]  copy2D (int[][] a)
  {
    int[][] b = new int [a.length][a[0].length];
    for (int i = 0; i < a.length; i++)
    {
      for (int j = 0; j < a[i].length; j++)
      {
        b[i][j] = a[i][j];
      }
    }
    return b;

  }

  public static int sum2D (int[][] a) { int sum = 0;
    for (int i = 0; i < a.length; i++)
    {
      for (int j = 0; j < a[i].length; j++)
      {
        sum += a[i][j];
      }
    }
    return sum;
  }

  public static void main (String[] args)
  {

  }
}