제출 #403650

#제출 시각아이디문제언어결과실행 시간메모리
403650salehCalvinball championship (CEOI15_teams)C++17
70 / 100
379 ms972 KiB
#include <bits/stdc++.h>


using namespace std;


const int MAXN = 10 * 1000 + 23, D = 1000 * 1000 + 7;















int dp[2][MAXN], a[MAXN], n, cnt[MAXN], jav;



int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr), cout.tie(nullptr);
	cin >> n;
	for (int i = 0; i < n; i++) cin >> a[i];
	{
		set<int> s;
		for (int i = 0; i < n; i++) {
			s.insert(a[i]);
			cnt[i] = s.size();
		}
	}
	fill(dp[1], dp[1] + n, 1);
	for (int i = 0; i < n - 1; i++) {
		for (int j = 1; j < n - 1; j++) dp[i & 1][j] = (dp[1 - (i & 1)][j] * j % D + dp[1 - (i & 1)][j + 1]) % D;
		int j = n - i - 1;
		jav += (a[j] - 1) * dp[1 - (i & 1)][cnt[j - 1]] % D;
		jav %= D;
	}
	cout << jav + 1;
	return 0;
}
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