Submission #261257

#	Time	Username	Problem	Language	Result	Execution time	Memory
261257		Berted	Cryptography (NOI20_crypto)	C++14	100 / 100	119 ms	9284 KiB

Crypto

#include <iostream>
#include <algorithm>
#define pii pair<int, int>
#define ll long long
#define fst first
#define snd second
using namespace std;
const ll MD = (1e9) + 7;
int n;
pii ar[300001] = {};
ll fkt[300001] = {}, rs = 0;
int fwk[300001] = {};
void upd(int x)
{
	for (; x <= n; x += x & (-x)) {fwk[x]++;}
}	
int query(int x)
{
	int to = 0;
	for (; x; x -= x & (-x)) {to += fwk[x];}
	return to;
}
int main()
{
	ios :: sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> n;
	fkt[0] = 1;
	for (int i = 1; i <= n; i++) {fkt[i] = (fkt[i - 1] * i) % MD;}
	for (int i = 0; i < n; i++)
	{
		cin >> ar[i].fst;
		ar[i].snd = i;
	}
	sort(ar, ar + n);
	for (int i = 0; i < n; i++)
	{
		rs += (fkt[n - 1 - ar[i].snd] * (i - query(ar[i].snd))) % MD;
		rs %= MD;
		upd(ar[i].snd + 1);
	}
	cout << (rs + 1) % MD << "\n";
	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