Problem p03353 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const double pi = acos(-1);
#define FOR(i, a, b) for (ll i = (a), __last_##i = (b); i < __last_##i; i++)
#define RFOR(i, a, b) for (ll i = (b)-1, __last_##i = (a); i >= __last_##i; i--)
#define REP(i, n) FOR(i, 0, n)
#define RREP(i, n) RFOR(i, 0, n)
#define __GET_MACRO3(_1, _2, _3, NAME, ...) NAME
#define rep(...) __GET_MACRO3(__VA_ARGS__, FOR, REP)(__VA_ARGS__)
#define rrep(...) __GET_MACRO3(__VA_ARGS__, RFOR, RREP)(__VA_ARGS__)
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  REP(i, v.size()) {
    if (i)
      os << " ";
    os << v[i];
  }
  return os;
}
template <typename T>
ostream &operator<<(ostream &os, const vector<vector<T>> &v) {
  REP(i, v.size()) {
    if (i)
      os << endl;
    os << v[i];
  }
  return os;
}

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

const int dx4[4] = {1, 0, -1, 0};
const int dy4[4] = {0, 1, 0, -1};

const int dx8[8] = {1, 1, 0, -1, -1, -1, 0, 1};
const int dy8[8] = {0, 1, 1, 1, 0, -1, -1, -1};

vector<vector<int>> Graph;
vector<int> value;

int main(int argc, const char *argv[]) {

  // remove the bottom 3 lines when you submit this code.
  std::ifstream in("sample.txt");
  std::cin.rdbuf(in.rdbuf());

  cin.tie(0);
  ios::sync_with_stdio(false);

  string s;
  cin >> s;
  int k;
  cin >> k;

  map<string, int> submap{};
  priority_queue<string, vector<string>, greater<string>> que{};

  for (int i = 0; i < (int)s.size(); i++) {
    for (int j = 1; j <= (int)s.size() - i; j++) {

      if (!submap.count(s.substr(i, j))) {
        submap.insert(make_pair(s.substr(i, j), 0));
        que.push(s.substr(i, j));
      }
    }
  }

  rep(i, k) {
    if (i == k - 1)
      cout << que.top() << endl;
    que.pop();
  }
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const double pi = acos(-1);
#define FOR(i, a, b) for (ll i = (a), __last_##i = (b); i < __last_##i; i++)
#define RFOR(i, a, b) for (ll i = (b)-1, __last_##i = (a); i >= __last_##i; i--)
#define REP(i, n) FOR(i, 0, n)
#define RREP(i, n) RFOR(i, 0, n)
#define __GET_MACRO3(_1, _2, _3, NAME, ...) NAME
#define rep(...) __GET_MACRO3(__VA_ARGS__, FOR, REP)(__VA_ARGS__)
#define rrep(...) __GET_MACRO3(__VA_ARGS__, RFOR, RREP)(__VA_ARGS__)
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  REP(i, v.size()) {
    if (i)
      os << " ";
    os << v[i];
  }
  return os;
}
template <typename T>
ostream &operator<<(ostream &os, const vector<vector<T>> &v) {
  REP(i, v.size()) {
    if (i)
      os << endl;
    os << v[i];
  }
  return os;
}

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

const int dx4[4] = {1, 0, -1, 0};
const int dy4[4] = {0, 1, 0, -1};

const int dx8[8] = {1, 1, 0, -1, -1, -1, 0, 1};
const int dy8[8] = {0, 1, 1, 1, 0, -1, -1, -1};

vector<vector<int>> Graph;
vector<int> value;

int main(int argc, const char *argv[]) {

  // remove the bottom 3 lines when you submit this code.
  std::ifstream in("sample.txt");
  std::cin.rdbuf(in.rdbuf());

  cin.tie(0);
  ios::sync_with_stdio(false);

  string s;
  cin >> s;
  int k;
  cin >> k;

  map<string, int> submap{};
  priority_queue<string, vector<string>, greater<string>> que{};

  for (int i = 0; i < (int)s.size(); i++) {
    for (int j = 1; j <= (int)s.size() - i; j++) {
      if (s.substr(i, j).size() > 10)
        continue;
      if (!submap.count(s.substr(i, j))) {
        submap.insert(make_pair(s.substr(i, j), 0));
        que.push(s.substr(i, j));
      }
    }
  }

  rep(i, k) {
    if (i == k - 1)
      cout << que.top() << endl;
    que.pop();
  }
}