#495385 (C++17) No.1011 Infinite Stairs

• 問題: No.1011 Infinite Stairs
• ユーザー: imoni_kawaii
• 提出日時: 2020-06-12 13:35:02
• 言語: C++17 (gcc 12.3.0 + boost 1.83.0)
• 結果: AC
• 実行時間: 35 ms / 2,000 ms
• コード長: 2,855 bytes
• コンパイル時間: 2,066 ms
• コンパイル使用メモリ: 206,544 KB
• 実行使用メモリ: 34,684 KB
• 最終ジャッジ日時: 2024-07-17 12:09:53
• 合計ジャッジ時間: 3,842 ms
• ジャッジサーバーID （参考情報）: judge3 / judge1

入力	結果	実行時間; 実行使用メモリ
testcase_00	AC	32 ms; 34,648 KB
testcase_01	AC	33 ms; 34,592 KB
testcase_02	AC	35 ms; 34,616 KB
testcase_03	AC	34 ms; 34,524 KB
testcase_04	AC	33 ms; 34,620 KB
testcase_05	AC	33 ms; 34,512 KB
testcase_06	AC	33 ms; 34,576 KB
testcase_07	AC	34 ms; 34,540 KB
testcase_08	AC	34 ms; 34,456 KB
testcase_09	AC	32 ms; 34,520 KB
testcase_10	AC	33 ms; 34,456 KB
testcase_11	AC	33 ms; 34,480 KB
testcase_12	AC	33 ms; 34,448 KB
testcase_13	AC	33 ms; 34,520 KB
testcase_14	AC	34 ms; 34,480 KB
testcase_15	AC	34 ms; 34,544 KB
testcase_16	AC	33 ms; 34,664 KB
testcase_17	AC	33 ms; 34,684 KB
testcase_18	AC	33 ms; 34,448 KB
testcase_19	AC	32 ms; 34,620 KB
testcase_20	AC	33 ms; 34,604 KB
testcase_21	AC	33 ms; 34,616 KB
testcase_22	AC	32 ms; 34,676 KB
testcase_23	AC	32 ms; 34,544 KB
testcase_24	AC	33 ms; 34,684 KB
testcase_25	AC	32 ms; 34,632 KB
testcase_26	AC	33 ms; 34,576 KB

ソースコード

#include <bits/stdc++.h>
#ifdef _DEBUG
#include "debug.hpp"
#else
#define debug(...)
#endif
#define REP(i, m, n) for(int i = (int)(m); i < (int)(n); ++i)
#define rep(i, n) REP(i, 0, n)
using namespace std;
using ll = long long;
using ld = long double;
using pll = pair<ll, ll>;
template<class T, class U> inline bool chmax(T &a, const U &b) { if(a < b) { a = b; return true; } return false; }
template<class T, class U> inline bool chmin(T &a, const U &b) { if(a > b) { a = b; return true; } return false; }

constexpr int MAX_N = 2010101;
constexpr int MOD = 1e9+7;
//constexpr int MOD = 998244353;

struct mint {
long long x;
  mint(long long x = 0) noexcept : x((x%MOD + MOD) % MOD) {}

  // basis
  mint operator-() const { return mint(-x); }
  mint& operator+=(const mint a) noexcept { if((x += a.x) >= MOD) x -= MOD; return *this; }
  mint& operator-=(const mint a) noexcept { if((x += MOD-a.x) >= MOD) x -= MOD; return *this; }
  mint& operator*=(const mint a) noexcept { (x *= a.x) %= MOD; return *this; }
  mint operator+(const mint a) const noexcept { return mint(*this) += a; }
  mint operator-(const mint a) const noexcept { return mint(*this) -= a; }
  mint operator*(const mint a) const noexcept { return mint(*this) *= a; }
  mint mpow(long long t) const noexcept {
    if(!t) return 1;
    mint a = mpow(t>>1);
    a *= a;
    if(t&1) a *= *this;
    return a;
  }

  // for prime MOD
  mint inv() const noexcept { return mpow(MOD-2); }
  mint& operator/=(const mint a) noexcept { return *this *= a.inv(); }
  mint operator/(const mint a) const noexcept { return mint(*this) /= a; }

  // comparison
  bool operator==(const mint &a) const noexcept { return this->x == a.x; }
  bool operator!=(const mint &a) const noexcept { return this->x != a.x; }

  // I/O stream
  friend istream& operator>>(istream& is, mint& a) noexcept { return is >> a.x; }
  friend ostream& operator<<(ostream& os, const mint& a) noexcept { return os << a.x; }
};
// additional
mint mpow(const long long &a, ll n) noexcept { return mint(a).mpow(n); }
mint mpow(const mint &a, ll n) noexcept { return a.mpow(n); }

struct combination {
  vector<mint> fac, ifac;
  combination(int n) : fac(n+1), ifac(n+1) {
    assert(n < MOD);
    fac[0] = 1;
    for(int i = 1; i <= n; ++i) fac[i] = fac[i-1]*i;
    ifac[n] = fac[n].inv();
    for(int i = n; i >= 1; --i) ifac[i-1] = ifac[i]*i;
  }
  mint operator()(int n, int k) {
    if(k < 0 || k > n) return 0;
    return fac[n]*ifac[k]*ifac[n-k];
  }
} com(MAX_N);
mint fac(int n) { assert(0 <= n && n <= MAX_N); return com.fac[n]; }
mint ifac(int n) { assert(0 <= n && n <= MAX_N); return com.ifac[n]; }


int main() {
  cin.tie(0); ios::sync_with_stdio(false);
  ll n, d, k;
  cin >> n >> d >> k;
  mint ans = 0;
  rep(i, n+1) {
    ans += mpow(-1, i)*com(n, i)*com(k-d*i-1, n-1);
  }
  cout << ans << '\n';
  return 0;
}