Need some help with method I was working on i need to return HighestColumn index of Jagged 2d array as a int

Question

what I need to do

getHighestInColumnIndex

public static int getHighestInColumnIndex(double[][] data,

int col)

Returns index of the largest element of the selected column in the two dimensional array index 0 refers to the first column. If a

row in the two dimensional array doesn't have this column index, it is not an error, it doesn't participate in this method.

Parameters:

data - the two dimensional array

col - the column index to find the largest element of (0 refers to the first column)

Returns:

the index of the largest element of the column

my code:

public static int getHighestInColumnIndex(double[][] data, int col) {

double max = data[0][col];

int location = -1;

for(int i =0; i<data.length; i++) {

if(col>= 0 && col<data[i].length) 

if(data[i][col]>max) {

max = data[i][col];

location = i;

}

}

return location;

}

Answer 1

You're still on the right track...

one problem is the intatlization statement:

double max = data[0][col];

It's possible that the column could not exist in the first row, leading to crash and burn.

You must initialize the max to some gross negative value which guarantees the

first available array element will become the max.

Otherwise I agree with your logic.

I moved the max value var to a private data member and provided a getter; the function now returns the INDEX of the largest element in the column. The results are correct for this test data. Both the column max

and it's index are output

I am a bit perturbed that the browser is messing up the columns in the array declaration. It's clean

as a whistle in notepad.

---------------------------------

class AngieARaggedArrays

{

public static final int MAX_COLUMNS=6;

private static double maxValue;

double GetMaxValue() { return(maxValue); }

/*********************************************

Returns the largest column value or -1

************************************************/

public static int getHighestInColumn(double[][]data, int col)

{

maxValue=-999999;

int iIndexPosOfMax=-1;

for (int rowLoop=0; rowLoop<data.length; rowLoop++)

{

if (

(col>=0) && (col<data[rowLoop].length)

)

// Then that column EXISTS in this particular row

{

if ( data[rowLoop][col]>maxValue) //the current max value has been DEFEATED!!

{ // new champion ;-)

maxValue = data[rowLoop][col];

iIndexPosOfMax = rowLoop;

}

}

}

return(iIndexPosOfMax);

}

public static void main(String args[])

{

double A[][] = { {5, 4, 3, 2, 1},

{4, 3, 2},

{1, 4, 7, 9, 3, 5},

{7, 8, 4, 1, 2},

{9, 3},

{1, 3, 3, 4, 5},

{2},

{7, 6, 5, 4}

};

AngieARaggedArrays x = new AngieARaggedArrays();

for (int columnLoop=0; columnLoop<x.MAX_COLUMNS; columnLoop++)

{

int iIndexPos = x.getHighestInColumn(A,columnLoop);

double maxValue = x.GetMaxValue();

System.out.println(" The highest value in column " + columnLoop

+ " is : " + maxValue

+ " which is at index position "+iIndexPos

);

}

}

}