Problem p00776 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
using namespace std;
/*{{{*/ // template
#define rep(i, n) for (int i = 0; i < n; i++)
constexpr int INF = numeric_limits<int>::max() / 2;
constexpr long long LINF = numeric_limits<long long>::max() / 3;
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(v) (v).begin(), (v).end()
#define sz(x) (int)(x).size()
#define debug(x) cerr << #x << ":" << x << endl
#define debug2(x, y) cerr << #x << "," << #y ":" << x << "," << y << endl
// struct fin{ fin(){ cin.tie(0); ios::sync_with_stdio(false); } } fin_;
struct Double {
  double d;
  explicit Double(double x) : d(x) {}
};
ostream &operator<<(ostream &os, const Double x) {
  os << fixed << setprecision(20) << x.d;
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) {
  os << "[";
  for (const auto &v : vec) {
    os << v << ",";
  }
  os << "]";
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << "(" << p.first << "," << p.second << ")";
  return os;
}
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
// constexpr double eps = 1e-14;
constexpr double eps = 1e-10;
constexpr ll mod = 1e9 + 7;
const int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};
/*}}}*/

string s;
int n;
array<char, 26> alf;
vector<string> ans;

template <typename T> ostream &operator<<(ostream &os, const set<T> &st) {
  os << "{";
  for (T v : st)
    os << v << ",";
  os << "}";
  return os;
}

string fx(const string &v) {
  string t = v;
  bool used[26];
  fill(used, used + 26, false);
  for (int i = 0; i < n; i++) {
    if (t[i] == 'a')
      continue;
    if (!used[t[i] - 'a']) {
      t[i]--;
    }
    used[v[i] - 'a'] = true;
  }
  return t;
}

void solve() {
  ans.assign(0, "");
  n = s.size();

  for (int mask = 0; mask < (1 << n); mask++) {
    string ss = s;
    bool f = true;
    bool exist[26];
    fill(exist, exist + 26, false);
    for (int i = 0; i < n; i++) {
      if (mask & (1 << i)) {
        if (ss[i] == 'z') {
          f = false;
          break;
        }
        ss[i]++;
        if (exist[ss[i] - 'a']) {
          f = false;
          break;
        }
      }
      exist[ss[i] - 'a'] = true;
    }

    if (!f) {
      // ss = s;
      // for(int i=0;i<n;i++){
      //     if(mask & (1<<i)) ss[i]++;
      // }
      // cout << ss << endl;
      continue;
    }
    string fs = fx(ss);
    // cout << ss << " " << fs << endl;
    if (fs == s)
      ans.pb(ss);
  }
  sort(all(ans));

  cout << ans.size() << endl;
  if (ans.size() <= 10) {
    for (auto x : ans)
      cout << x << endl;
    return;
  }
  for (int i = 0; i < 5; i++)
    cout << ans[i] << endl;
  for (int i = ans.size() - 5; i < ans.size(); i++)
    cout << ans[i] << endl;
}

void init() {
  for (int i = 0; i < 26; i++) {
    alf[i] = i + 'a';
  }
}

int main() {
  while (1) {
    cin >> s;
    if (s == "#")
      break;
    solve();
  }
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
/*{{{*/ // template
#define rep(i, n) for (int i = 0; i < n; i++)
constexpr int INF = numeric_limits<int>::max() / 2;
constexpr long long LINF = numeric_limits<long long>::max() / 3;
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(v) (v).begin(), (v).end()
#define sz(x) (int)(x).size()
#define debug(x) cerr << #x << ":" << x << endl
#define debug2(x, y) cerr << #x << "," << #y ":" << x << "," << y << endl
// struct fin{ fin(){ cin.tie(0); ios::sync_with_stdio(false); } } fin_;
struct Double {
  double d;
  explicit Double(double x) : d(x) {}
};
ostream &operator<<(ostream &os, const Double x) {
  os << fixed << setprecision(20) << x.d;
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) {
  os << "[";
  for (const auto &v : vec) {
    os << v << ",";
  }
  os << "]";
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << "(" << p.first << "," << p.second << ")";
  return os;
}
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
// constexpr double eps = 1e-14;
constexpr double eps = 1e-10;
constexpr ll mod = 1e9 + 7;
const int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};
/*}}}*/

string s;
int n;
array<char, 26> alf;
vector<string> ans;

template <typename T> ostream &operator<<(ostream &os, const set<T> &st) {
  os << "{";
  for (T v : st)
    os << v << ",";
  os << "}";
  return os;
}

string fx(const string &v) {
  string t = v;
  bool used[26];
  fill(used, used + 26, false);
  for (int i = 0; i < n; i++) {
    if (t[i] == 'a')
      continue;
    if (!used[t[i] - 'a']) {
      t[i]--;
    }
    used[v[i] - 'a'] = true;
  }
  return t;
}

void solve() {
  ans.assign(0, "");
  n = s.size();

  for (int mask = 0; mask < (1 << n); mask++) {
    string ss = s;
    bool f = true;
    bool used[26];
    fill(used, used + 26, false);
    rep(i, n) if (mask & (1 << i)) {
      if (used[ss[i] - 'a']) {
        f = false;
        break;
      }
      if (ss[i] == 'z') {
        f = false;
        break;
      }
      used[ss[i] - 'a'] = true;
      ss[i] += 1;
      if (ss[i] == 'a') {
        f = false;
        break;
      }
    }
    if (!f)
      continue;
    string fs = fx(ss);
    // cout << ss << " " << fs << endl;
    if (fs == s)
      ans.pb(ss);
  }
  sort(all(ans));

  cout << ans.size() << endl;
  if (ans.size() <= 10) {
    for (auto x : ans)
      cout << x << endl;
    return;
  }
  for (int i = 0; i < 5; i++)
    cout << ans[i] << endl;
  for (int i = ans.size() - 5; i < ans.size(); i++)
    cout << ans[i] << endl;
}

void init() {
  for (int i = 0; i < 26; i++) {
    alf[i] = i + 'a';
  }
}

int main() {
  while (1) {
    cin >> s;
    if (s == "#")
      break;
    solve();
  }
}