Submission #948359

#	Time	Username	Problem	Language	Result	Execution time	Memory
948359		Lilypad	Cryptography (NOI20_crypto)	C++14	100 / 100	346 ms	31572 KiB

Crypto

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<ll,ll>
#define pb push_back
#define fi first
#define se second

const ll N = 3e5+3;
const ll MOD = 1e9+7;

ll a[N],b[N],fac[N],bit[N];
ll n,tmp,ans;
map<ll,ll> mp;

void update(ll idx) {
	for(int i=idx; i<=n; i+=i&-i) {
		bit[i]++;
	}
}

ll query(ll idx) {
	ll ret = 0;
	for(int i=idx; i>=1; i-=i&-i) {
		ret += bit[i];
	}
	return ret;
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin >> n;
	fac[0] = 1;
	for(int i=1; i<=n; i++) {
		cin >> a[i];
		b[i] = a[i];
		fac[i] = fac[i-1] * i;
		fac[i] %= MOD;
	}
	sort(b+1,b+n+1);
	for(int i=1; i<=n; i++) {
		mp[b[i]] = i;
	}
	for(int i=1; i<=n; i++) a[i] = mp[a[i]];
	for(int i=n; i>=1; i--) {
		ans += (fac[n-i] * query(a[i]-1)) % MOD;
		ans %= MOD;
		update(a[i]);
	}
	cout << (ans + 1) % MOD << endl;
}

• 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