main.cpp

#include <iostream>
const int n = 2, m = 3;
int main()
{
   int arr[n][m] = { { 3, 5, 4 }, { 8, 6, 9 } };
   for ( auto& row : arr )
   {
      for ( auto col : row )
      {
         std::cout << col << " "; // 3 5 4 8 6 9
      }
   }
   return 0;
}