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

#include <algorithm>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
// #define LOG(...)
#define FOR(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())
#define RSORT(c) sort((c).rbegin(), (c).rend())
#define CLR(a) memset((a), 0, sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, 1, 0, -1};

struct UnionFind {
  vector<int> v;
  UnionFind(int n) : v(n) {
    for (int i = 0; i < n; i++)
      v[i] = i;
  }
  int find(int x) { return v[x] == x ? x : v[x] = find(v[x]); }
  void unite(int x, int y) { v[find(x)] = find(y); }
};

string ango(string s) {
  REP(i, 25) {
    size_t t = s.find('b' + i);
    if (t != string::npos) {
      s[t]--;
    }
  }
  return s;
}
string in;
vector<string> ans;
void saiki(string s, int idx) {
  if (idx == s.size()) {
    string s2 = ango(s);
    if (in == s2) {
      ans.push_back(s);
    }
    return;
  }

  if (idx > 0) {
    if (ango(s).substr(0, idx) != in.substr(0, idx))
      return;
  }

  saiki(s, idx + 1);
  if (s[idx] != 'z')
    s[idx]++;
  saiki(s, idx + 1);
}

int main() {
  while (cin >> in, in != "#") {
    ans.clear();
    saiki(in, 0);
    SORT(ans);
    ans.erase(unique(ALL(ans)), ans.end());
    cout << ans.size() << endl;
    if (ans.size() <= 10) {
      REP(i, ans.size())
      cout << ans[i] << endl;
    } else {
      REP(i, 5)
      cout << ans[i] << endl;
      REP(i, 5)
      cout << ans[ans.size() - 5 + i] << endl;
    }
  }
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
// #define LOG(...)
#define FOR(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())
#define RSORT(c) sort((c).rbegin(), (c).rend())
#define CLR(a) memset((a), 0, sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, 1, 0, -1};

struct UnionFind {
  vector<int> v;
  UnionFind(int n) : v(n) {
    for (int i = 0; i < n; i++)
      v[i] = i;
  }
  int find(int x) { return v[x] == x ? x : v[x] = find(v[x]); }
  void unite(int x, int y) { v[find(x)] = find(y); }
};

string ango(string s) {
  REP(i, 25) {
    size_t t = s.find('b' + i);
    if (t != string::npos) {
      s[t]--;
    }
  }
  return s;
}
string in;
vector<string> ans;
void saiki(string s, int idx) {
  if (idx == s.size()) {
    string s2 = ango(s);
    if (in == s2) {
      ans.push_back(s);
    }
    return;
  }
  saiki(s, idx + 1);
  if (s[idx] != 'z')
    s[idx]++;
  saiki(s, idx + 1);
}

int main() {
  while (cin >> in, in != "#") {
    ans.clear();
    saiki(in, 0);
    SORT(ans);
    cout << ans.size() << endl;
    if (ans.size() <= 10) {
      REP(i, ans.size())
      cout << ans[i] << endl;
    } else {
      REP(i, 5)
      cout << ans[i] << endl;
      REP(i, 5)
      cout << ans[ans.size() - 5 + i] << endl;
    }
  }
}