Submission #973099

#	Time	Username	Problem	Language	Result	Execution time	Memory
973099		jadai007	Cryptography (NOI20_crypto)	C++17	100 / 100	536 ms	43532 KiB

Crypto

#include<bits/stdc++.h>
#define int long long

using namespace std;

const int mod = 1e9 + 7;
set<int> s;
map<int, int> mt;
int arr[300300], n, cnt = 1, fac[300300], fw[300300], ans = 1;

void update(int idx, int val){
    for(int i = idx; i<=n; i+=(i&-i)) fw[i]+=val;
}

int query(int idx){
    int sum = 0;
    for(int i = idx; i>0; i-=(i&-i)) sum+=fw[i];
    return sum;
}

int32_t main(){
    cin.tie(nullptr)->sync_with_stdio(false);
    cin >> n;
    fac[0] = 1;
    for(int i = 1; i<=n; ++i) fac[i] = (fac[i - 1]*i)%mod;
    for(int i = 1; i<=n; ++i) cin >> arr[i], s.insert(arr[i]);
    for(auto x:s) mt[x] = cnt++;
    for(int i = 1; i<=n; ++i){
        ans = (ans + fac[n - i]*(mt[arr[i]] - query(mt[arr[i]]) - 1)%mod)%mod;
        update(mt[arr[i]], 1);
    }
    cout << ans;
}

• 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