Thread: help 2d array confusion

int [] [] matrix = {
    {16, 3, 2, 13},
    {5, 10, 11, 8},
    {2, 6, 7, 12},
    {2, 15, 14, 1}
};
 
 
 
result = 0;
for(row = 3 ; row > 3; row--){
    result = matrix[row][row] +result;
        }
sumDiag2 = result;
if (sumDiag2 == magic){
     System.out.println("Minor Diagonal  = "+ result +  "  OK");}
else
    System.out.println("Minor Diagonal = "+ result + "  NOT OK");
 
 
    }
}

ok so i have this code i want to add the minor diagonals which should be 32 (13,11,6,2)
but i keep getting 0... i dont get it help

for(row = 3 ; row > 3; row--){
    result = matrix[row][row] +result;
        }

This will never go through the for loop as row is already 3, which means that it already is not greater than 3.

That might be part of the problem.

So result will still be 0?

result = 0;
for(row = 3 ; row >= 0; row--){
    result = matrix[row][row] +result;
        }
sumDiag2 = result;
if (sumDiag2 == magic){
     System.out.println("Minor Diagonal  = "+ sumDiag2 +  "  OK");}
else
    System.out.println("Minor Diagonal = "+ sumDiag2 + "  NOT OK");

oh darn i overlooked sorry so i changed it to row >= 0
now it just displays 34 when it supposed to display 32

i dont understand its supposed to add
matrix[3][3] because the value of row starts at 3
but it keeps computing the value of the major diagonal (matrix[0][0])

for(row = 3 ; row >= 0; row--){
result = matrix[row][row] +result;
}

First iteration x = 3
result = matrix[3][3];
Second iteration x = 2
result = matrix[3][3] + matrix[2][2];
Third iteration x = 1
result = matrix[3][3]+ matrix[2][2] + matrix[1][1];
Fourth iteration x = 0;
result = matrix[3][3] + matrix[2][2] + matrix[1][1] + matrix[0][0];

So result should be

1 + 7 + 10 + 16
= 34

I could think that perhaps an array of results


result[0] = matrix[3][3];
result[1]= result[0] + matrix[2][2];
result[2] = result[1] + matrix[1][1];
result[3] = result[2] + matrix[0][0];

for (int x = 0; x < =3; x++)
{
if (x ==0)
result[x] = matrix[3-x][3-x];
 
else
{
result[x] = result[x-1] + matrix[3-x][3-x];
}
}

Now check if result[3] = magic.