제출 #62532

#제출 시각아이디문제언어결과실행 시간메모리
62532MatheusLealVCalvinball championship (CEOI15_teams)C++17
100 / 100
843 ms1464 KiB
#include <bits/stdc++.h>
#define N 10001
using namespace std;
typedef long long ll;

int n, k, v[N], tot, used[N], mod = 1000007;

int dp[2][N], pref[N];

int solve(int i, int k)
{
	if(i > n) return 1;

	if(dp[i][k] != -1) return dp[i][k];

	ll A = (((ll)solve(i + 1, k) * (ll)k) % mod + solve(i + 1, k + 1) % mod)%mod;

	return dp[i][k] = A;
}

inline int pos()
{
	set<int> add;

	for(int i = 1; i <= n; i++)
	{
		pref[i] = add.size();

		add.insert(v[i]);
	}

	int A = (n + 1)%2, B = n%2;

	for(int i = n + 1; i >= 1; i--)
	{
		if(i >= 2)
		{
			for(int k = i; k >= 1; k--)
			{
				if(i > n) dp[A][k] = 1;

				else
				{
					dp[A][k] = ((ll)k * dp[B][k])%mod;

					dp[A][k] += dp[B][k + 1];

					if(dp[A][k] >= mod) dp[A][k] -= mod;
				}
			}
		}

		if(i <= n)
		{
			tot = (tot + dp[B][ pref[i] ]*(v[i] - 1LL))%mod;
		}

		swap(A, B);
	}

	return (tot + 1)%mod;
}

int main()
{
	ios::sync_with_stdio(false); cin.tie(0);

	cin>>n;

	for(int i = 1; i <= n; i++) cin>>v[i];

	cout<<pos()<<"\n";
}
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