Is there a way to sum an 2d array diagonally? - multidimensional-array

Question

Im trying to make it where the values in my 2d array add up from diagonally top left to bottom right and top right to bottom left. I'm having trouble thinking what to do. I'm thinking maybe a for loop would be in there but thats all I think. I also have an accumulator too. My question is referring to my lefttoright and righttoleft functions. Thanks!
#include <iostream>
using namespace std;
const int COLS = 3;
bool showarray(const int[][COLS]);
int sumofrow(const int[][COLS]);
int sumofcolumn(const int[][COLS]);
int lefttoright(const int[][COLS]); // function to sum diagonally
int righttoleft(const int[][COLS]); // function to sum diagonally
int main()
{
int table1[COLS][COLS] = { 1,2,3,4,5,6,7,8,9 };
int table2[COLS][COLS] = { {4, 9, 2},
{3, 5, 7},
{8, 1, 6} };
cout << "ARRAY\n";
cout << (showarray(table1) ? " " : " NOT ");
cout << "a LO Shu Magic Square!"
<< endl;
}
int sumofrow(const int arry[][COLS])
{
int total;
for (int i = 0; i < COLS; i++)
{
total = 0;
for (int count = 0; count < COLS; count++)
{
total += arry[i][count];
}
}
return total;
}
int sumofcolumn(const int arry[][COLS])
{
int total;
for (int col = 0; col < COLS; col++)
{
total = 0;
for (int row = 0; row < COLS; row++)
{
total += arry[col][row];
}
}
return total;
}
int lefttoright(const int arry[][COLS])
{
int total = 0;
// for loop possibly?
return total;
}
int righttoleft(const int arry[][COLS])
{
int total = 0;
// for loop here possibly?
return total;
}