Lecture Notes on 20 Mar 2013


public class TestArray
{
  // print the sum of each row in a 2-D array
  public static void rowSum (int[][] a)
  {
    for (int i = 0; i < a.length; i++)
    {
      int sum = 0;
      for (int j = 0; j < a[i].length; j++)
      {
        sum += a[i][j];
      }
      System.out.println (sum);
    }
  }

  // print the sum of each column in a 2-D array
  public static void colSum (int[][] a)
  {
    for (int j = 0; j < a[0].length; j++)
    {
      int sum = 0;
      for (int i = 0; i < a.length; i++)
      {
        sum += a[i][j];
      }
      System.out.println (sum);
    }
  }

  // transpose a 2-D array
  public static int[][] transpose (int[][] a)
  {
    int[][] b = new int[a[0].length][a.length];
    for (int i = 0; i < b.length; i++)
    {
      for (int j = 0; j < b[i].length; j++)
      {
        b[i][j] = a[j][i];
      }
    }
    return b;
  }

  // add two matrices together
  public static int[][] addMatrix (int[][] a, int[][] b)
  {
    int[][] c = new int [a.length][a[0].length];

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

  // compute the dot product of two vectors
  public static int dotProduct (int[][] a, int[][] b)
  {

  }


  // find the max in a 2-D array
  public static int max (int[][] a)
  {
    int maxVal = a[0][0];
    for (int i = 0; i < a.length; i++)
    {
      for (int j = 0; j < a[i].length; j++)
      {
        if (a[i][j] > maxVal)
	  maxVal = a[i][j];
      }
    }
    return maxVal;
  }

  public static void main (String[] args)
  {

  }
}