Submission #4018004

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Source Code Expand

#include <iostream>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <map>
#include <queue>

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

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

template<typename T>
T extgcd(T a, T b, T &x ,T &y){
    for (T u = y = 1, v = x = 0; a; ) {
        ll q = b/a;
        swap(x -= q*u, u);
        swap(y -= q*v, v);
        swap(b -= q*a, a);
    }
    return b;
}

template<typename T>
T mod_inv(T x, T m){
    T s, t;
    extgcd(x, m, s, t);
    return (m+s)% m;
}

template <class T>
T pow_ (T x, T n, T M){
    uint64_t u = 1, xx = x;
    while (n > 0){
        if (n&1) u = u * xx % M;
        xx = xx * xx % M;
        n >>= 1;
    }
    return static_cast<T>(u);
};
template <class T> class Factorial {
    T mod;
    vector<uint64_t> facts, factinv;

public:
    Factorial(int n, T mod) : facts(static_cast<u32>(n+1)), factinv(static_cast<u32>(n+1)), mod(mod) {
        facts[0] = 1;
        for (int i = 1; i < n+1; ++i) facts[i] = facts[i-1]*i % mod;
        factinv[n] = pow_(facts[n], static_cast<uint64_t>(mod - 2), static_cast<uint64_t>(mod));
        for (int i = n-1; i >= 0; --i) factinv[i] = factinv[i+1] * (i+1) % mod;
    }

    T fact(int k) const {
        if(k >= 0) return static_cast<T>(facts[k]);
        else return static_cast<T>(factinv[-k]);
    }

    T operator[](const int &k) const {
        if(k >= 0) return static_cast<T>(facts[k]);
        else return static_cast<T>(factinv[-k]);
    }

    T C(int p, int q) const {
        if(q < 0 || p < q) return 0;
        return static_cast<T>(facts[p]*  factinv[q] % mod * factinv[p-q] % mod);
    }

    T P(int p, int q) const {
        if(q < 0 || p < q) return 0;
        return static_cast<T>((facts[p] * factinv[p-q]) % mod);
    }

    T H(int p, int q) const {
        if(p < 0 || q < 0) return 0;
        return static_cast<T>(q == 0 ? 1 : C(p+q-1, q));
    }
};


int main() {
    int n;
    cin >> n;
    vector<ll> v(n);
    for (auto &&i : v) scanf("%lld", &i);
    Factorial<ll> fa(n, MOD);
    vector<int> s(n+1, 0);
    for (int i = 1; i <= n; ++i) {
        s[i] = (s[i-1]+mod_inv(i+1, MOD)) % MOD;

    }
    ll ans = 0;
    for (int i = 0; i < n; ++i) {
        (ans += ((v[i]*(1+ s[n-i-1]+s[i]))%MOD * fa[n])) %= MOD;
    }
    cout << ans << "\n";
    return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:87:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     for (auto &&i : v) scanf("%lld", &i);
                                         ^

Judge Result