Submission #676486

#	Time	Username	Problem	Language	Result	Execution time	Memory
676486		penguin133	Cryptography (NOI20_crypto)	C++17	100 / 100	93 ms	10344 KiB

Crypto

#include <bits/stdc++.h>
using namespace std;
int ft[300005];
pair<int, int> d[300005];
int n;
int ls(int x){
	return x & (-x);
}
void update(int p, int v){
	for(;p<=n;p+=ls(p)){
		ft[p] += v;
	}
}
void update1(int p){
	for(;p<=n;p+=ls(p))ft[p] = 0;
}
int query(int p){
	int sum = 0;
	for(;p;p-=ls(p)){
		sum += ft[p];
	}
	return sum;
}
int main(){
    ios::sync_with_stdio(0);cin.tie(0);
	cin >> n;
	int arr[n+1];
	long long f[n+1];
	f[1] = 1;
	f[0] = 0;
	for(int i=1;i<=n;i++)cin >> arr[i];
	for(int i=1;i<=n;i++)update(i, 1);
	for(int i=2;i<=n;i++)f[i] = (i * f[i-1])%1000000007; 
	for(int i = 1; i <= n; i++){
		d[i].first = arr[i];
		d[i].second = i;
	}
	sort(d + 1, d + n + 1);
	int cnt2 = 1;
	for(int i = 1; i <= n; i++){
		if (i > 1 && d[i].first != d[i-1].first) cnt2++;
		arr[d[i].second] = cnt2;
	}
	long long cnt = 1;
	for(int i=1;i<=n;i++){
		int e = arr[i];
		cnt += f[n-i] * (query(e)- 1);
		cnt %= 1000000007;
		update(e, -1);
	}
	cout << cnt;
}

• 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