#include <iostream>
#include <vector>
int main ()
{
std::vector<std::vector<int>> v {
{1, 2, 3, 4},
{5, 6, 7, 8},
{9, 10, 11, 12}
};
for (int i = 0; i < v.size(); i++) {
for (int j = 0; j < v[0].size(); j++) {
std::cout << v[i][j] << " ";
}
std::cout << "\n";
}
return 0;
}
/*
run:
1 2 3 4
5 6 7 8
9 10 11 12
*/