Problem p03089 (C++)

Buggy submission (status: Time Limit Exceeded):
#include "bits/stdc++.h"
using namespace std;
#ifdef _DEBUG
#include "dump.hpp"
#else
#define dump(...)
#endif

#define int long long
#define rep(i, a, b) for (int i = (a); i < (b); i++)
#define rrep(i, a, b) for (int i = (b)-1; i >= (a); i--)
#define all(c) begin(c), end(c)
const int INF =
    sizeof(int) == sizeof(long long) ? 0x3f3f3f3f3f3f3f3fLL : 0x3f3f3f3f;
const int MOD = 1000000007;
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return true;
  }
  return false;
}

template <typename T> vector<T> gen_v(size_t a) { return vector<T>(a); }
template <typename T, typename... Ts> auto gen_v(size_t a, Ts... ts) {
  return vector<decltype(gen_v<T>(ts...))>(a, gen_v<T>(ts...));
}
template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type fill_v(T &t, const V &v) {
  t = v;
}
template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type fill_v(T &t, const V &v) {
  for (auto &e : t)
    fill_v(e, v);
}

vector<int> dfs(vector<int> b) {
  if (b.size() == 0)
    return vector<int>{-1};
  dump(b);
  rep(j, 0, b.size()) {
    if (b[j] > j + 1)
      return vector<int>();
    if (b[j] == j + 1) {
      vector<int> c = b;
      c.erase(c.begin() + j);
      auto res = dfs(c);
      if (res.size() == 0)
        continue;
      res.push_back(j);
      return res;
    }
  }
  return vector<int>();
}

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N;
  cin >> N;
  vector<int> b(N);
  rep(i, 0, N) { cin >> b[i]; }
  vector<int> a = dfs(b);

  dump(a);

  if (a.size()) {
    rep(i, 1, a.size()) { cout << a[i] + 1 << endl; }
  } else {
    cout << -1 << endl;
  }

  return 0;
}

Fixed submission:
#include "bits/stdc++.h"
using namespace std;
#ifdef _DEBUG
#include "dump.hpp"
#else
#define dump(...)
#endif

#define int long long
#define rep(i, a, b) for (int i = (a); i < (b); i++)
#define rrep(i, a, b) for (int i = (b)-1; i >= (a); i--)
#define all(c) begin(c), end(c)
const int INF =
    sizeof(int) == sizeof(long long) ? 0x3f3f3f3f3f3f3f3fLL : 0x3f3f3f3f;
const int MOD = 1000000007;
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return true;
  }
  return false;
}

template <typename T> vector<T> gen_v(size_t a) { return vector<T>(a); }
template <typename T, typename... Ts> auto gen_v(size_t a, Ts... ts) {
  return vector<decltype(gen_v<T>(ts...))>(a, gen_v<T>(ts...));
}
template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type fill_v(T &t, const V &v) {
  t = v;
}
template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type fill_v(T &t, const V &v) {
  for (auto &e : t)
    fill_v(e, v);
}

vector<int> dfs(vector<int> b) {
  if (b.size() == 0)
    return vector<int>{-1};
  dump(b);
  rep(j, 0, b.size()) {
    if (b[j] > j + 1)
      return vector<int>();
  }
  rep(j, 0, b.size()) {
    if (b[j] == j + 1) {
      vector<int> c = b;
      c.erase(c.begin() + j);
      auto res = dfs(c);
      if (res.size() == 0)
        continue;
      res.push_back(j);
      return res;
    }
  }
  return vector<int>();
}

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N;
  cin >> N;
  vector<int> b(N);
  rep(i, 0, N) { cin >> b[i]; }
  vector<int> a = dfs(b);

  dump(a);

  if (a.size()) {
    rep(i, 1, a.size()) { cout << a[i] + 1 << endl; }
  } else {
    cout << -1 << endl;
  }

  return 0;
}