結果

問題 No.1885 Flat Permutation
コンテスト
ユーザー nrvft
提出日時 2022-03-25 22:24:10
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 6 ms / 2,000 ms
コード長 4,347 bytes
コンパイル時間 2,255 ms
コンパイル使用メモリ 194,964 KB
最終ジャッジ日時 2025-01-28 12:16:59
ジャッジサーバーID
（参考情報） 		judge3 / judge3
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ファイルパターン 結果
sample AC * 4
other AC * 43
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 # 

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using vl = vector<ll>;
template<class T> using vc = vector<T>;
template<class T> using vvc = vector<vector<T>>;

#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define repr(i, n) for (ll i = (n)-1; i >= 0; i--)
#define repe(i, l, r) for (ll i = (l); i < (r); i++)
#define reper(i, l, r) for (ll i = (r)-1; i >= (l); i--)
#define repa(i,n) for (auto& i: n)

template<class T1, class T2> inline bool chmax(T1 &a, const T2 &b) {if (a<b) { a=b; return 1;} return 0;}
template<class T1, class T2> inline bool chmin(T1 &a, const T2 &b) {if (b<a) { a=b; return 1;} return 0;}
struct init{init(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);cerr<<fixed<<setprecision(15);}}init_;

#ifdef DEBUG
template <class T> void verr(const set<T> &st) { repa(a, st) cerr << a << " "; cerr << endl; }
template <class S, class T> void verr(const map<S, T> &mp) { repa(a, mp) cerr << "{" << a.first << ", " << a.second << "} "; cerr << endl; }
template <class S, class T, class N> void verr(const vector<pair<S,T>>& a, const N& n) { rep(i, n) cerr << "{" << a[i].first << ", " << a[i].second << "} "; cerr << endl; }
template <class T, class N> void verr(const vector<T>& a, const N& n) { rep(i, n) cerr << a[i] << " "; cerr << endl; }
ll dbgt = 1; void err() { cerr << "passed " << dbgt++ << endl; }
template<class H, class... T> void err(H&& h,T&&... t){ cerr<< h << (sizeof...(t)?" ":"\n") << flush; if(sizeof...(t)>0) err(forward<T>(t)...); }
#endif

const ll INF = 4e18;
const ld EPS = 1e-11;
const ld PI = acos(-1.0L);
// const ll MOD = 1e9 + 7;
const ll MOD = 998244353;
//--------------------------------------------------------------------------------//
// modint
template <int _MOD>
struct modint {
    long long val;
    static const int mod = _MOD;
    modint(long long v = 0) noexcept : val(v % mod) {
        if (val < 0) val += mod;
    }
    inline modint operator - () const noexcept {
        return val ? mod - val : 0;
    }
    inline modint operator + (const modint& r) const noexcept { return modint(*this) += r; }
    inline modint operator - (const modint& r) const noexcept { return modint(*this) -= r; }
    inline modint operator * (const modint& r) const noexcept { return modint(*this) *= r; }
    inline modint operator / (const modint& r) const noexcept { return modint(*this) /= r; }
    inline modint& operator += (const modint& r) noexcept {
        val += r.val;
        if (val >= mod) val -= mod;
        return *this;
    }
    inline modint& operator -= (const modint& r) noexcept {
        val -= r.val;
        if (val < 0) val += mod;
        return *this;
    }
    inline modint& operator *= (const modint& r) noexcept {
        val = val * r.val % mod;
        return *this;
    }
    inline modint& operator /= (const modint& r) noexcept {
        long long a = r.val, b = mod, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b; swap(a, b);
            u -= t * v; swap(u, v);
        }
        val = val * u % mod;
        if (val < 0) val += mod;
        return *this;
    }
    inline bool operator == (const modint& r) const noexcept {
        return this->val == r.val;
    }
    inline bool operator != (const modint& r) const noexcept {
        return this->val != r.val;
    }
    inline friend ostream& operator << (ostream &os, const modint& x) noexcept {
        return os << x.val;
    }
    inline friend istream& operator >> (istream &is, modint& x) noexcept {
        is >> x.val;
        x = modint(x.val);
        return is;
    }
    inline friend modint modpow(const modint &a, long long n) noexcept {
        modint t = 1, v = a;
        while(n){
            if (n & 1) t *= v;
            v *= v;
            n >>= 1;
        }
        return t;
    }
};
using mint = modint<MOD>;

int main() {
    ll N, X, Y;
    cin >> N >> X >> Y;
    if (X > Y) swap(X, Y);

    if(Y - X == 1 and X > 1 and Y < N) {
        cout << 0 << endl;
        return 0;
    }

    ll n = Y - X - 2;
    if (X == 1) n++;
    if (Y == N) n++;

    vc<mint> dp(n + 1);
    dp[0] = 1;
    rep(i, n) {
        dp[i + 1] += dp[i];
        if(i + 3 <= n) dp[i + 3] += dp[i];
    }

    cout << dp[n] << endl;
}
0