What is the optimal way of printing a 2d array vector - c++

Question

I have a function which receive a 2D vector of char from another class and print it
void dat_Output::print_All(Board *board)
{
int x;
int y;
x = 0;
y = 0;
while(x < 26)
{
while(y < 59)
{
std::cout << board->get_Board()[x][y];
y++;
}
std::cout << std::endl;
y = 0;
x++;
}
}
here is the get_Board() function
std::vector<std::vector<char> > Board::get_Board()
{
return(board);
}
My question is for resource efficiency which is the better should I make a copy of the vector at the start of my printing function to avoid calling get_Board() 26*59 time? and whats the difference on resource consuming?

Answer 1

If get_Board() must return a copy, make a single copy before the loops (instead of 26 * 59 copies), and work directly on it. It will also avoid you the board-> indirection.
If possible, return a const reference instead of a copy from get_Board()
Assuming you want to print the entire board, don't use nested while loops, you can use nested for-range loops and avoid explicit indexing.
Minimal example :
#include <iostream>
#include <vector>
class X
{
public :
X() : v({ { 'a', 'b'} , { 'a', 'b' } , { 'c', 'd' } }) {}
const std::vector<std::vector<char>> & GetVector() const { return v; }
private:
std::vector<std::vector<char> > v;
};
int main() {
X x;
const std::vector<std::vector<char> >& v = x.GetVector();
for(auto& v2 : v)
for(auto& c : v2)
std::cout << c << ' ';
}

Answer 2

void dat_Output::print_All(Board *board)
{
std::vector<std::vector<char> > myboard = board->get_Board()[x][y];
int x;
int y;
x = 0;
y = 0;
while(x < 26)
{
while(y < 59)
{
std::cout << myboard[x][y];
y++;
}
std::cout << std::endl;
y = 0;
x++;
}
}
I would create a copy initially. I think every time you call get_Board() you would return a array of vector of vectors and this would be hit on the performance, while calling it once would be cheaper.