Simple Matrix

#include <chrono>
#include <iostream>
#include <random>
#include <vector>
using namespace std;
void foo(vector<double> a, int n) {
  int i = 0;
  for (auto& e : a) {
    cout << e << ' ';
    if (++i % n == 0) cout << endl;
  }
}
int main() {
  int n;
  cin >> n;
  mt19937 g(chrono::system_clock::now().time_since_epoch().count());
  uniform_real_distribution<double> rnd(0., 1.);
  vector<double> box(n * n);
  for (auto& e : box)
    e = rnd(g);
  foo(box, n);
}