// AP Computer Science, A Exam, 1996, Question 4, part A in C++
// also AB Exam, question 2

int SumCross(const Mat & m, int R, int C)
// precondition: 0 <= R < m.rows; 0 <= C < m.cols
{
    int sum = 0;
    int j;

    // sum down the C-th column
    
    for(j=0; j < m.rows; j++)
    {
	sum += m.entries[j][C];
    }

    // sum across the R-th row

    for(j=0; j < m.cols; j++)
    {
	sum += m.entries[R][j];
    }

    // subtract m.entries[R][C] which was summed twice

    sum -= m.entries[R][C];

    return sum;
    
}