結果

問題 No.1489 Repeat Cumulative Sum
ユーザー m_tsubasa
提出日時 2021-04-23 22:48:53
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 151 ms / 2,000 ms
コード長 3,586 bytes
コンパイル時間 2,060 ms
コンパイル使用メモリ 198,192 KB
最終ジャッジ日時 2025-01-21 00:16:10
ジャッジサーバーID
(参考情報)
judge3 / judge2
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ファイルパターン 結果
sample AC * 3
other AC * 27
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;
template <int mod = (int)(1e9 + 7)>
struct ModInt {
int x;
ModInt() : x(0) {}
ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
ModInt &operator+=(const ModInt &p) {
if ((x += p.x) >= mod) x -= mod;
return *this;
}
ModInt &operator-=(const ModInt &p) {
if ((x += mod - p.x) >= mod) x -= mod;
return *this;
}
ModInt &operator*=(const ModInt &p) {
x = (int)(1LL * x * p.x % mod);
return *this;
}
ModInt &operator/=(const ModInt &p) {
*this *= p.inverse();
return *this;
}
ModInt operator-() const { return ModInt(-x); }
ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
bool operator==(const ModInt &p) const { return x == p.x; }
bool operator!=(const ModInt &p) const { return x != p.x; }
ModInt inverse() const {
int a = x, b = mod, u = 1, v = 0, t;
while (b > 0) {
t = a / b;
swap(a -= t * b, b);
swap(u -= t * v, v);
}
return ModInt(u);
}
ModInt pow(int64_t n) const {
ModInt res(1), mul(x);
while (n) {
if (n & 1) res *= mul;
mul *= mul;
n >>= 1;
}
return res;
}
friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x; }
friend istream &operator>>(istream &is, ModInt &a) {
int64_t t;
is >> t;
a = ModInt<mod>(t);
return (is);
}
static int get_mod() { return mod; }
};
struct Combination {
vector<ModInt<>> _fact, _rfact, _inv;
Combination(long long nsize = 5000000)
: _fact(nsize + 1), _rfact(nsize + 1), _inv(nsize + 1) {
_fact[0] = _rfact[nsize] = _inv[0] = 1;
for (int i = 1; i <= nsize; i++) _fact[i] = _fact[i - 1] * i;
_rfact[nsize] /= _fact[nsize];
for (int i = nsize - 1; i >= 0; i--) _rfact[i] = _rfact[i + 1] * (i + 1);
for (int i = 1; i <= nsize; i++) _inv[i] = _rfact[i] * _fact[i - 1];
}
inline ModInt<> fact(int k) const { return _fact[k]; }
inline ModInt<> rfact(int k) const { return _rfact[k]; }
inline ModInt<> inv(int k) const { return _inv[k]; }
ModInt<> P(int n, int r) const {
if (r < 0 || n < r) return 0;
return fact(n) * rfact(n - r);
}
ModInt<> C(int p, int q) const {
if (q < 0 || p < q) return 0;
return fact(p) * rfact(q) * rfact(p - q);
}
ModInt<> largeC(long long p, long long q) const {
if (q < 0 || p < q) return 0;
if (q >= (long long)_fact.size()) q = p - q;
// if (q >= (long long)5000) q = p - q;
ModInt<> res = rfact(q);
for (int i = 0; i < q; ++i) res *= p - i;
return res;
}
// n types,choose r
ModInt<> H(int n, int r) const {
if (n < 0 || r < 0) return (0);
return r == 0 ? 1 : C(n + r - 1, r);
}
ModInt<> largeH(long long n, long long r) const {
if (n < 0 || r < 0) return (0);
return r == 0 ? 1 : largeC(n + r - 1, r);
}
ModInt<> Catalan(int n) {
// C(2n,n) / (n + 1)
return fact(2 * n) * rfact(n + 1) * rfact(n);
}
};
using mint = ModInt<>;
long long n, m;
vector<mint> a;
Combination com;
mint solve();
int main() {
cin >> n >> m, --n;
a.resize(n);
for (auto &p : a) cin >> p;
cout << solve() << endl;
return 0;
}
mint solve() {
mint res = 0, now = 1;
reverse(a.begin(), a.end());
for (int i = 0; i < n; ++i) {
now *= i + m;
now /= i + 1;
res += now * a[i];
}
return res;
}
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