help with magic square

[Mike Currier]

Hi everyone,
I was working on this and ran into a problem. When i try to find the sum of the columns and rows it goes and adds all of the numbers in the array instead of one column/row at a time. Is there a way I can modify my code to make it so it will return the sum of a single row/column to determine if its magic. Thanks.

import java.util.*;

public class Square {

    ArrayList<Integer> data;
    
    public Square() {
        data = new ArrayList<Integer>();
    }

    // this method is complete
    public void add(int i) {
        data.add(i);
    }

    // implement this method
    public boolean isMagic() {
        int squareSize = (int) Math.ceil(Math.sqrt(data.size()));
        int [][] matrix = new int [squareSize][squareSize];
        int dataIdx = 0;
        for(  int rowIdx = 0; rowIdx  < squareSize; ++ rowIdx ) {
            for( int colIdx = 0; colIdx < squareSize; ++ colIdx ) {
                matrix[rowIdx] [colIdx] = data.get(dataIdx);
                ++ dataIdx;
            }
        }
        // main diagonal sum
        int diagSum = 0;
        for( int k = 0; k < squareSize; ++ k ) {
            diagSum += matrix[k][k];
        }
        // reverse diagonal sum
        int revDiagSum = 0;
        for( int k = 0; k < squareSize; ++ k ) {
            revDiagSum += matrix[squareSize-k-1][k];
        }
        
        //row sum
        int rowSum = 0;
        int j = 0;
        while(j < squareSize){
        	for(int k = 0; k < squareSize; ++k){
        		rowSum += matrix[j][k];
        	}
        	j++;
        }
        
        //column sum
        int colSum = 0;
        int y = 0;
        while(y < squareSize){
        	for(int k = 0; k < squareSize; ++k){
        		colSum += matrix[k][y];
        	}
        	y++;
        }
        if(colSum == rowSum && diagSum == revDiagSum && rowSum == diagSum && colSum == revDiagSum){
        	return true;
        }
        else{
        	return false;
        }
    }

    // implement this method
    public String toString() {
        int squareSize = (int) Math.ceil(Math.sqrt(data.size()));
        StringBuilder sb = new StringBuilder();
        for( int k = 0; k < data.size(); ++k ) {
            String number = String.format("%4d", data.get(k));
            sb.append(number);
            if( (k + 1) % squareSize == 0 ) {
                sb.append("\n");
            }
        }
        sb.append("\n");
        return sb.toString();
    }
}

[Paul Clapham]

Mike Currier wrote:When i try to find the sum of the columns and rows it goes and adds all of the numbers in the array instead of one column/row at a time.

Yes, that's right, it does.

Is there a way I can modify my code to make it so it will return the sum of a single row/column to determine if its magic.

Sure. But are you sure that's what you want to do? I thought the rule was that each row and each column had to add up to the magic number. So just choosing one row and one column wouldn't be an adequate test, would it?

Seems to me that you want to return all of the row sums and all of the column sums. In that case returning a single number for rowSum and a single number for columnSum is the wrong design; you want to return an array of numbers for each of those things.

[Winston Gutkowski]

Mike Currier wrote:Is there a way I can modify my code to make it so it will return the sum of a single row/column to determine if its magic.

Not an answer, but a general tip: create methods to do what you want, eg:
public int rowSum(int row, int[][] array) { ...
and then call them from your isMagic() method.

Creating methods helps to isolate logic, which hopefully makes things clearer for you (and also makes things easier to test).

HIH

Winston