Sorting Two-Dimensional Array by Row

Question

The requirement is to sort the rows of a two-dimensional array. I feel like my code is very close to being done, but I can't figure out why it isn't displaying the sorted array. I forgot to mention that we are not allowed to use the premade sorting methods. The problem is most likely in the sortRows method. Anyways, here's my code:

public class RowSorting
{
   public static void main(String[] args) 
{
  double[][] numbers  = new double[3][3];
  double[][] number  = new double[3][3];
  int run = 0;
  String answer = "";

  while (run == 0)
     {
       Scanner input = new Scanner(System.in);
       System.out.print("Enter a 3-by-3 matrix row by row: ");
       for(int row = 0; row < numbers.length; row++)
        {
         for(int column = 0; column < numbers[row].length; column++)
          {
           numbers[row][column] = input.nextDouble();
          }
        }
       for(int row = 0; row < numbers.length; row++)
        {
         for(int column = 0; column < numbers[row].length; column++)
          {
           System.out.print(numbers[row][column] + " ");
          }
         System.out.print("\n");
        } 
       System.out.println("The sorted array is: \n");
       number = sortRows(numbers);
       for(int row = 0; row < number.length; row++)
        {
         for(int column = 0; column < number[row].length; column++)
          {
           System.out.print(number[row][column] + " ");
          }
         System.out.print("\n");
        } 




   System.out.print("\nWould you like to continue the program (y for yes or    anything else exits): ");
       answer = input.next();

       if(answer.equals("y"))
        {
         continue;
        }
       else
         break;
      }




}
 public static double[][] sortRows(double[][] m)
{
  for(int j = 0; j < m[j].length - 1; j++)
   {
    for(int i = 0; i < m.length; i++)
    {
      double currentMin = m[j][i];
      int currentMinIndex = i;

      for(int k = i + 1; k < m[j].length; k++)
      {
       if(currentMin > m[j][i])
       {
        currentMin = m[j][i];
        currentMinIndex = k;
       }
      }
    if(currentMinIndex != i)
    {
     m[currentMinIndex][j] = m[j][i];
     m[j][i] = currentMin;
    }
    }
   }
  return m;
 }
}

ergonaut · Accepted Answer · 2015-11-08 02:42:47Z

1

It looks like this block:

if(currentMin > m[j][i])
   {
    currentMin = m[j][i];
    currentMinIndex = k;
   }

Will never happen. Because you just assigned currentMin to m[j][i] two lines before it. I believe you want to use k in that if check. Something like

if (currentMin > m[j][k]){
    currentMin = m[j][k];
    currentMinIndex = k;
}

answered Nov 8, 2015 at 2:42

ergonaut

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1 Comment

Austin P Over a year ago

Oh yes! Thank you so much. This fixed part of my problem, but I was able to play around with it to figure it out. I also had to flip the currentMinIndex variable and j. Thank you so much!!!

rc242 · Accepted Answer · 2015-11-08 03:17:19Z

0

As cited per ergonaut, you have a problem with the codeblock

if(currentMin > m[j][i]) ...

and also

m[currentMinIndex][j] = m[j][i];

However, you also have a problem with your for-loops.

for(int j = 0; j < m[j].length - 1; j++) ...
    for(int i = 0; i < m.length; i++) ...

Both of these are oddly structured. You probably want to swap these for-loops so that you don't throw index exceptions. This will also cause you address the indices in your code. And modify your j-index for-loop to include the entire range.

edited Nov 8, 2015 at 3:17

answered Nov 8, 2015 at 3:11

rc242

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