Submission #1285693

#	Time	Username	Problem	Language	Result	Execution time	Memory
1285693		jackofall718	Cryptography (NOI20_crypto)	C++20	100 / 100	252 ms	28616 KiB

Crypto

#include <bits/stdc++.h>
#include <chrono>
#define ll long long int
#define endl '\n'
#define vn vector<ll>
#define vi vector<pair <ll,ll>>

using namespace std;
using namespace std::chrono;
const int MAX_N = 1e9 + 7;
#define pii pair<ll,ll>
const ll INF = 0x3f3f3f3f3f3f3f3f;

#define pb push_back  
#define srt(vp) sort(vp.begin(), vp.end())

struct fenwick{

    vn bit;
    ll n;
    fenwick(ll size){//no void here
        bit.assign(size+1,0);
        n=size;//imp
        for (int i = 1; i <= n; i++) update_internal(i);//imp
    };

    void update_internal(ll i) {
        for (; i <= n; i += i & -i) bit[i] += 1;
    }

    void update(ll i){
        for (;i<=n;i += i&-i)bit[i]-=1;
    }
    ll query(ll i){
        
        
        ll res = 0;
        for (;i>0;i-= i&-i)res += bit[i];
        return res;
    }



};

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

    auto start = high_resolution_clock::now();

    ll n;
    cin>>n;
    vn v(n);
    for (auto &x:v)cin>>x;
    vn arr = v;


    vn exp (n+1);
    exp[0]=1;
    for (int i=1;i<=n;i++){
        exp[i]=(exp[i-1]*i)%MAX_N;

    }
    sort(arr.begin(),arr.end());
    arr.erase(unique(arr.begin(),arr.end()),arr.end());
    map <ll,ll> pos;
    for (int i=0;i<arr.size();i++){
        pos[arr[i]]=i+1;
    }
    for(int i=0;i<n;i++){
        v[i]=pos[v[i]];
    }
    fenwick tree(arr.size());
    ll ans = 0;
    for (int i=0;i<n;i++){
        ll index = i+1;
        ll base = tree.query(v[i]-1);
        
        ll other = exp[n-index];
        
        if (base)ans = (ans + (base * other) % MAX_N) % MAX_N;
        tree.update(v[i]);
        
        
        

    }
   cout << (ans + 1) % MAX_N;//imp



    

    auto stop = high_resolution_clock::now();
    auto duration = duration_cast<microseconds>(stop - start);
    //cout << "Time taken by function: " << duration.count() << " microseconds" << endl;

    return 0;
}

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