結果

問題 No.1740 Alone 'a'
ユーザー okuraofvegetabl
提出日時 2021-11-12 22:02:40
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 120 ms / 2,000 ms
コード長 4,527 bytes
コンパイル時間 2,196 ms
コンパイル使用メモリ 203,304 KB
最終ジャッジ日時 2025-01-25 16:47:18
ジャッジサーバーID
（参考情報） 		judge2 / judge3
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 38
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

#include <bits/stdc++.h>
using namespace std;
#define eps 1e-9
#define INF 2000000000              // 2e9
#define LLINF 2000000000000000000ll // 2e18 (llmax:9e18)
#define all(x) (x).begin(), (x).end()
#define sq(x) ((x) * (x))
#define rep(i, x) for (int i = 0; i < (int)(x); i++)
#define drep(i, x) for (int i = ((int)(x)-1); i >= 0; i--)
#define popcount __builtin_popcount
#define next __next
#define prev __prev
#ifndef LOCAL
#define dmp(...) ;
#else
#define dmp(...)                                                               \
  cerr << "[ " << #__VA_ARGS__ << " ] : " << dump_str(__VA_ARGS__) << endl
#endif
// ---------------- Utility ------------------
template <class T>
bool chmin(T &a, const T &b) {
  if (a <= b) return false;
  a = b;
  return true;
}
template <class T>
bool chmax(T &a, const T &b) {
  if (a >= b) return false;
  a = b;
  return true;
}
template <class T>
using MaxHeap = priority_queue<T>;
template <class T>
using MinHeap = priority_queue<T, vector<T>, greater<T>>;
template <class T>
vector<T> vect(int len, T elem) {
  return vector<T>(len, elem);
}
// ----------------- Input -------------------
template <class T, class U>
istream &operator>>(istream &is, pair<T, U> &p) {
  return is >> p.first >> p.second;
}
template <class T>
istream &operator>>(istream &is, vector<T> &vec) {
  for (int i = 0; i < vec.size(); i++) is >> vec[i];
  return is;
}
// ----------------- Output ------------------
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  return os << p.first << ',' << p.second;
}
template <class T>
ostream &operator<<(ostream &os, const vector<T> &v) {
  for (const T &e : v) os << e << " ";
  return os;
}
template <class T>
ostream &operator<<(ostream &os, const deque<T> &d) {
  for (const T &e : d) os << e << " ";
  return os;
}
template <class T>
ostream &operator<<(ostream &os, const set<T> &s) {
  os << "{ ";
  for (const T &e : s) os << e << " ";
  return os << "}";
}
template <class T, class U>
ostream &operator<<(ostream &os, const map<T, U> &m) {
  os << "{ ";
  for (const auto &[key, val] : m) os << "( " << key << " -> " << val << " ) ";
  return os << "}";
}
template <class TupleTy, size_t... I>
void dump_tuple(ostream &os, const TupleTy t, std::index_sequence<I...>) {
  (..., (os << (I == 0 ? "" : ",") << std::get<I>(t)));
}
template <class... Args>
ostream &operator<<(ostream &os, const tuple<Args...> &t) {
  os << "(";
  dump_tuple(os, t, std::make_index_sequence<sizeof...(Args)>());
  return os << ")";
}
void dump_str_rec(ostringstream &) {}
template <class Head, class... Tail>
void dump_str_rec(ostringstream &oss, Head &&head, Tail &&... tail) {
  oss << ", " << head;
  dump_str_rec(oss, forward<Tail>(tail)...);
}
template <class T, class... U>
string dump_str(T &&arg, U &&... args) {
  ostringstream oss;
  oss << arg;
  dump_str_rec(oss, forward<U>(args)...);
  return oss.str();
}
// --------------- Fast I/O ------------------
void fastio() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);
}
// ------------------ ACL --------------------
#include <atcoder/modint>
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
using mint = atcoder::static_modint<MOD>;
ostream &operator<<(ostream &os, const mint &v) {
  return os << v.val();
}
// ------------ End of template --------------
#define endl "\n"
using ll = long long;
using pii = pair<int, int>;
const bool multitest = false;
void solve() {
  int N;
  string S;
  cin >> N >> S;
  auto dp = vect(N + 1, vect(2, vect(2, mint(0))));
  dp[0][1][0] = mint(1);
  for (int i = 0; i < N; i++) {
    {
      // tight
      for (char c = 'a'; c <= S[i]; c++) {
        for (int k = 0; k < 2; k++) {
          int nj = (c == S[i]);
          int nk = k + (c == 'a' ? 1 : 0);
          if (nk > 1) continue;
          dp[i + 1][nj][nk] += dp[i][1][k];
        }
      }
      for (char c = 'a'; c <= 'z'; c++) {
        for (int k = 0; k < 2; k++) {
          int nk = k + (c == 'a' ? 1 : 0);
          if (nk > 1) continue;
          dp[i + 1][0][nk] += dp[i][0][k];
        }
      }
    }
  }
  mint ans = dp[N][0][1] + dp[N][1][1];
  int acnt = 0;
  for (int i = 0; i < N; i++)
    if (S[i] == 'a') acnt++;
  if (acnt == 1) ans -= mint(1);
  cout << ans << endl;
  return;
}
int main() {
  fastio();
  if (!multitest) {
    solve();
  } else {
    cerr << "[Warning] Multi testcase mode on" << endl;
    int t;
    cin >> t;
    while (t--) solve();
  }
  return 0;
}
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