Problem p04044 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#define fastio                                                                 \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define all(x) (x).begin(), (x).end()
#define rep(i, a, b) for (int i = a; i < b; i++)
#define endl '\n'
#define MAX 1000000
#define debug(x...)                                                            \
  cerr << "[" << #x << "] = [";                                                \
  _print(x)
typedef long long int ll;
using namespace std;

void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template <typename T, typename V> void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T> void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x)
    cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V> void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v))
    cerr << ", ";
  _print(v...);
}

const ll mod = 1e9 + 7;
const double eps = 1e-9;
const double pi = acos(-1);

void solve() {
  int n;
  cin >> n;
  vector<string> arr;
  for (int i = 0; i < n; ++i) {
    cin >> arr[i];
  }
  sort(all(arr));
  for (string i : arr)
    cout << i;
  cout << "\n";
}

int main() {
  fastio int test = 1;
  while (test--)
    solve();
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
#define fastio                                                                 \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define all(x) (x).begin(), (x).end()
#define rep(i, a, b) for (int i = a; i < b; i++)
#define endl '\n'
#define MAX 1000000
#define debug(x...)                                                            \
  cerr << "[" << #x << "] = [";                                                \
  _print(x)
typedef long long int ll;
using namespace std;

void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template <typename T, typename V> void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T> void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x)
    cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V> void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v))
    cerr << ", ";
  _print(v...);
}

const ll mod = 1e9 + 7;
const double eps = 1e-9;
const double pi = acos(-1);

void solve() {
  int n, l;
  cin >> n >> l;
  vector<string> arr(n);
  for (int i = 0; i < n; ++i) {
    cin >> arr[i];
  }
  sort(all(arr));
  for (string i : arr)
    cout << i;
  cout << "\n";
}

int main() {
  fastio int test = 1;
  while (test--)
    solve();
  return 0;
}