結果

問題 No.1102 Remnants
ユーザー firiexpfiriexp
提出日時 2020-07-03 22:18:03
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 73 ms / 2,000 ms
コード長 2,994 bytes
コンパイル時間 2,394 ms
コンパイル使用メモリ 100,936 KB
最終ジャッジ日時 2025-01-11 14:46:28
ジャッジサーバーID
（参考情報） 		judge3 / judge1
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 * 25
権限があれば一括ダウンロードができます
コンパイルメッセージ
main.cpp: In function ‘int main()’:
main.cpp:86:29: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   86 |     for (auto &&i : v) scanf("%d", &i);
      |                        ~~~~~^~~~~~~~~~

ソースコード

diff # 

#include <iostream>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = unsigned;
using u64 = unsigned long long;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max()/32*15+208;

template<u32 M = 1000000007>
struct modint{
    u32 val;
    modint(): val(0){}
    template<typename T>
    modint(T t){t %= (T)M; if(t < 0) t += (T)M; val = t;}

    modint pow(ll k) const {
        modint res(1), x(val);
        while(k){
            if(k&1) res *= x;
            x *= x;
            k >>= 1;
        }
        return res;
    }
    template<typename T>
    modint& operator=(T t){t %= (T)M; if(t < 0) t += (T)M; val = t; return *this;}
    modint inv() const {return pow(M-2);}
    modint& operator+=(modint a){val += a.val; if(val >= M) val -= M; return *this;}
    modint& operator-=(modint a){if(val < a.val) val += M-a.val; else val -= a.val; return *this;}
    modint& operator*=(modint a){val = (u64)val*a.val%M; return *this;}
    modint& operator/=(modint a){return (*this) *= a.inv();}
    modint operator+(modint a) const {return modint(val) +=a;}
    modint operator-(modint a) const {return modint(val) -=a;}
    modint operator*(modint a) const {return modint(val) *=a;}
    modint operator/(modint a) const {return modint(val) /=a;}
    modint operator-(){return modint(M-val);}
    bool operator==(const modint a) const {return val == a.val;}
    bool operator!=(const modint a) const {return val != a.val;}
    bool operator<(const modint a) const {return val < a.val;}
};
using mint = modint<MOD>;

class Factorial {
    vector<mint> facts, factinv;
public:
    explicit Factorial(int n) : facts(n+1), factinv(n+1) {
        facts[0] = 1;
        for (int i = 1; i < n+1; ++i) facts[i] = facts[i-1] * mint(i);
        factinv[n] = facts[n].inv();
        for (int i = n-1; i >= 0; --i) factinv[i] = factinv[i+1] * mint(i+1);
    }
    mint fact(int k) const {
        if(k >= 0) return facts[k]; else return factinv[-k];
    }
    mint operator[](const int &k) const {
        if(k >= 0) return facts[k]; else return factinv[-k];
    }
    mint C(int p, int q) const {
        if(q < 0 || p < q) return 0;
        return facts[p] * factinv[q] * factinv[p-q];
    }
    mint P(int p, int q) const {
        if(q < 0 || p < q) return 0;
        return facts[p] * factinv[p-q];
    }
    mint H(int p, int q) const {
        if(p < 0 || q < 0) return 0;
        return q == 0 ? 1 : C(p+q-1, q);
    }
};

int main() {
    int n, k;
    cin >> n >> k;
    vector<int> v(n);
    for (auto &&i : v) scanf("%d", &i);
    vector<mint> dp(n+1);
    dp[0] = 1;
    for (int i = 1; i <= n; ++i) {
        dp[i] = dp[i-1]*mint(k+i)*(mint(i).inv());
    }
    mint ans = 0;
    for (int i = 0; i < n; ++i) {
        ans += mint(v[i])*dp[i]*dp[n-i-1];
    }
    cout << ans.val << "\n";
    return 0;
}
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