Submission #1368645

#	Time	Username	Problem	Language	Result	Execution time	Memory
1368645		wyn	Cryptography (NOI20_crypto)	C++17	48 / 100	1095 ms	7392 KiB

Crypto

#include <bits/stdc++.h>
using namespace std;

int64_t N;
vector<int64_t> P;


/*
int64_t fact(int64_t n){
    int64_t ans = 1;
    for( auto i=2 ; i<=n ; i++ ){
        ans = ans*i % 1000000007;
    }
    return ans;
}
*/

vector<int64_t> fact;


int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);

    cin>>N;
    P.assign( N, 0 );
    for ( auto &p : P )
        cin >> p;

    fact = {1};
    fact.reserve(N);
    for( int i=1 ; i<=3e5 ; i++ ){
        fact.push_back(fact.back()*i%1000000007);
    }
    // for( int64_t i=0 ; i<=5 ; i++ ){
    //     cout << i << setw(5) << fact[i] << endl;
    // }

    int64_t ans = 1;
    for( int64_t i=0 ; i<N ; i++ ){
        int64_t smaller=0;
        for( int64_t j=i+1 ; j<N ; j++ ){
            if( P[j] < P[i] )
                smaller++;
        }

        ans += smaller*fact[N-i-1];
        ans %= 1000000007;
    }
    cout << ans << endl;

    return 0;
}

• Subtask 1: 5 / 5
• Subtask 2: 9 / 9
• Subtask 3: 0 / 10
• Subtask 4: 0 / 11
• Subtask 5: 21 / 21
• Subtask 6: 13 / 13
• Subtask 7: 0 / 19
• Subtask 8: 0 / 12