結果

問題 No.1275 綺麗な式
ユーザー 57tggx
提出日時 2020-09-21 15:48:41
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
RE  
(最新)
AC  
(最初)
実行時間 -
コード長 2,607 bytes
コンパイル時間 957 ms
コンパイル使用メモリ 69,536 KB
最終ジャッジ日時 2025-01-14 19:20:58
ジャッジサーバーID
（参考情報） 		judge3 / judge4
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 * 2
other AC * 12 RE * 48
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ソースコード

diff #
プレゼンテーションモードにする

#include <iostream>
#include <sys/stat.h>
#include <sys/mman.h>
template<class T, T MOD>
class Modint{
    T val;
public:
    Modint(T val = 0) : val(val % MOD + (val >= 0 ? 0 : MOD)) {}
    operator T(){ return val; }
    Modint &operator+=(const Modint &a){ val += a.val; if(val >= MOD) val -= MOD; return *this; }
    Modint &operator-=(const Modint &a){ val -= a.val; if(val < 0) val += MOD; return *this; }
    Modint &operator*=(const Modint &a){ val = val * a.val % MOD; return *this; }
    void inverse(){T x[2]={MOD,val},a[2]={0,1};int i;for(i=0;x[!i];i^=1){a[i]-=x[i]/x[!i]*a[!i];x[i]=x[i]%x[!i];}if(!i)a[i]+= MOD;val=a[i];}
    Modint &operator/=(Modint a){ a.inverse(); return *this *= a; }
    friend Modint modpow(Modint a, int n){ Modint ret(1); while(n){ if(n & 1) ret *= a; a *= a; n >>= 1; } return ret; }
    friend Modint operator+(Modint a, const Modint &b){ return a += b; }
    friend Modint operator-(Modint a, const Modint &b){ return a -= b; }
    friend Modint operator*(Modint a, const Modint &b){ return a *= b; }
    friend Modint operator/(Modint a, const Modint &b){ return a /= b; }
    friend std::ostream &operator<<(std::ostream &os, const Modint &a){ return os << a.val; }
};
using Int = long long;
using Mint = Modint<Int, 1000000007>;
int main(){
    struct stat stat;
    fstat(0, &stat);
    char *input = static_cast<char *>(mmap(NULL, stat.st_size, PROT_READ, MAP_PRIVATE, 0, 0));
    enum {
        num_a,
        num_b,
        num_n,
    } state = num_a;
    Int a = 0, b = 0, n = 0;
    for(int i = 0; i < stat.st_size; ++i){
        if(state == num_a){
            if(isdigit(input[i])){
                a = a * 10 + (input[i] - '0');
            }else if(input[i] == ' '){
                state = num_b;
            }else{
                return 0;
            }
        }else if(state == num_b){
            if(isdigit(input[i])){
                b = b * 10 + (input[i] - '0');
            }else if(input[i] == '\n'){
                state = num_n;
            }else{
                return 0;
            }
        }else if(state == num_n){
            if(isdigit(input[i])){
                n = n * 10 + (input[i] - '0');
            }else if(input[i] == '\n'){
                break;
            }else{
                return 0;
            }
        }
    }
    Mint array[512345];
    for(Int i = 0; i <= n / 2; ++i) array[i] = 1;
    {
        Mint tmp = 1;
        for(Int i = 0; i <= n / 2; ++i){
            array[i] *= tmp;
            tmp *= Mint(b);
        }
    }
    {
        Mint tmp = n % 2 ? a : 1;
        Mint square = Mint(a) * Mint(a);
        for(Int i = n / 2; i >= 0; --i){
            array[i] *= tmp;
            tmp *= square;
        }
    }
    {
        Mint tmp = 1;
        for(Int i = 0; i < n; ++i){
            if(i % 2 == 0) array[i / 2] *= tmp;
            tmp *= Mint(n - i);
            tmp /= Mint(i + 1);
        }
    }
    Mint ans = 0;
    for(Int i = 0; i <= n / 2; ++i){
//      std::cout << array[i] << std::endl;
        ans += array[i];
    }
    std::cout << ans * Mint(2) << std::endl;
}
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