結果

問題 No.2235 Line Up Colored Balls
ユーザー tsugutsugu
提出日時 2023-03-03 23:34:48
言語 C++14
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 13 ms / 2,000 ms
コード長 2,484 bytes
コンパイル時間 1,707 ms
コンパイル使用メモリ 170,008 KB
実行使用メモリ 6,144 KB
最終ジャッジ日時 2024-09-18 01:13:47
合計ジャッジ時間 3,737 ms
ジャッジサーバーID
（参考情報） 		judge2 / judge6
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 * 4
other AC * 55
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;
// const int mod = 998244353;
const int mod = 1000000007;
struct modint {
    long long a = 0;
    modint(long long x = 0) {while (x < 0) x += mod; a = x % mod;}
    modint(const modint &r) {a = r.a;}
    modint operator -(){return modint(-a);}
    modint operator +(const modint &r) {return modint(*this) += r;}
    modint operator -(const modint &r) {return modint(*this) -= r;}
    modint operator *(const modint &r) {return modint(*this) *= r;}
    modint &operator +=(const modint &r) {
      a += r.a;
      if(a >= mod) a -= mod;
      return *this;
    }
    modint &operator -=(const modint &r) {
        a -= r.a;
        if(a < 0) a += mod;
        return *this;
    }
    modint &operator *=(const modint &r) {
        a = a * r.a % mod;
        return *this;
    }
    modint pow(long long r) const {
        if (!r) return 1;
        modint x = pow(r >> 1);
        x *= x;
        if (r & 1) x *= *this;
        return x;
    }
    modint inverse() const {
        return pow(mod - 2);
    }
    modint& operator/=(const modint r) {
        return (*this) *= r.inverse();
    }
    modint operator/(const modint r) const {
        modint res(*this);
        return res /= r;
    }
};
 
istream &operator>>(istream &is, modint &x) {
    long long t;
    is >> t;
    x = t;
    return is;
}
ostream &operator<<(ostream &os, const modint& x) {
    return os << x.a;
}
const int MAX = 100044;
modint fac[MAX], inv[MAX], finv[MAX];
void cominit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for(int i = 2; i < MAX; i++) {
        fac[i] = fac[i - 1] * modint(i);
        inv[i] = - inv[mod % i] * modint(mod / i);
        finv[i] = finv[i - 1] * inv[i];
    }
}
modint Com(long long n, long long k) {
    if(n < k) return 0;
    if(n < 0 || k < 0) return 0;
    return fac[n] * finv[k] * finv[n - k];
}
modint Per(long long n, long long k) {
    if(n < k) return 0;
    if(n < 0 || k < 0) return 0;
    return fac[n] * finv[n - k];
}
 
using Mint = modint;
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;
    vector<int> x(n);
    for (int i = 0; i < n; i++) {
        cin >> x[i];
    }
    Mint sum = 0, sum2 = 0;
    for (int i = 0; i < n; i++) {
        sum += Mint(x[i]);
        sum2 += Mint(x[i]) * Mint(x[i]);
    }
    Mint S = Mint(accumulate(x.begin(), x.end(), 0));
    Mint ans = ((sum * sum - sum2) + S) / S;
    cout << ans << '\n';
}
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