#894508 (C++17) No.2388 At Least K-Characters

• 問題: No.2388 At Least K-Characters
• ユーザー: pitP
• 提出日時: 2023-07-22 11:50:41
• 言語: C++17 (gcc 13.3.0 + boost 1.87.0)
• 結果: AC
• 実行時間: 200 ms / 4,000 ms
• コード長: 2,803 bytes
• コンパイル時間: 3,671 ms
• コンパイル使用メモリ: 256,204 KB
• 最終ジャッジ日時: 2025-02-15 17:59:51
• ジャッジサーバーID （参考情報）: judge3 / judge5

ファイルパターン	結果
sample	AC * 3
other	AC * 34

ソースコード

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#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
istream &operator>>(istream &is, modint &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint &a) { return os << a.val(); }
istream &operator>>(istream &is, modint998244353 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint998244353 &a) { return os << a.val(); }
istream &operator>>(istream &is, modint1000000007 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint1000000007 &a) { return os << a.val(); } 
typedef long long ll;
typedef vector<vector<int>> Graph;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define rep(i,n) for (int i = 0;i < (int)(n); i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define my_sort(x) sort(x.begin(), x.end())
#define my_max(x) *max_element(all(x))
#define my_min(x) *min_element(all(x))
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF = (1<<30) - 1;
const ll LINF = (1LL<<62) - 1;
const int MOD = 998244353;
const int MOD2 = 1e9+7;
const double PI = acos(-1);
vector<int> di = {1,0,-1,0};
vector<int> dj = {0,1,0,-1};
#ifdef LOCAL
#  include <debug_print.hpp>
#  define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define debug(...) (static_cast<void>(0))
#endif
using mint = modint998244353;
int main(){
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    int N,M,K; cin >> N >> M >> K;
    string S; cin >> S;
    vector<vector<mint>> dp(M+1,vector<mint>(27));
    int cnt = 0;
    vector<bool> check(26, 0);
    dp[0][0] = 1;
    for(int i=0;i<M;i++){
        for(int j=0;j<=26;j++){
            mint v = dp[i][j];
            if (i < N && j == cnt){
                int res = 0;
                for(int l=0;l<(S[i] - 'a');l++){
                    if (check[l]) res++;
                }
                dp[i+1][j] += res;
                if (j+1 <= 26) dp[i+1][j+1] += (S[i] - 'a' - res);
                if (check[S[i] - 'a']) dp[i+1][j] += 1;
                else dp[i+1][j+1] += 1;
                v--; // S[0:i]を除く
            }
            if (i == N && j == cnt) {
                v--; // S[0:i]を除く
            }
            dp[i+1][j] += v * j;
            if (j+1<=26) dp[i+1][j+1] += v * (26-j);
        }
        if (i < N && !check[S[i] - 'a']){
            cnt++;
            check[S[i] - 'a'] = true;
        }
    }
    mint ans = 0;
    for(int i=1;i<=M;i++){
        for(int j=K;j<=26;j++){
            ans += dp[i][j];
        }
    }
    if (cnt >= K) ans--;
    cout << ans << endl;
}
 
 
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