In C++:

int diagonalDifference(vector> arr) { int n; n = end(arr)-begin(arr);// Find the lenght of the array.

cout << "n:" << n << endl; // error checking

//Declaration of sum variables
int sum_rtl =0;
int sum_ltr =0;

// Add up Left-to-Right
for(int i = 0; i < n; i++ )
{
    for(int j = 0; j < n; j++)
    {
        cout << "Before Sum LTR: " << arr[i][j] << endl;
        sum_ltr = sum_ltr + arr[i][j];
        i++;   
    }
    cout << "sum_ltr:"<<sum_ltr << endl;
}
//Add up Right-toLeft
for( int i = 0; i < n; i++)
{
    for(int j = n-1; j >= 0; j--)
    {
        cout << "Before Sum RTL: " << arr[i][j] << endl;
        sum_rtl = sum_rtl + arr[i][j];
        i++;    
    }    
    cout << "sum_rtl: " << sum_rtl << endl;
}
//Absolute value of the difference.
int diff = abs(sum_rtl - sum_ltr);

return diff;

}