제출 #138962

#제출 시각아이디문제언어결과실행 시간메모리
138962meatrowCalvinball championship (CEOI15_teams)C++17
10 / 100
106 ms65540 KiB
//#pragma GCC optimize("O3")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,tune=native")
//#pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;

const int N = 1e4;
int mod = 1e9 + 7;

int dp[N][N];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n;
    cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    int level = 1;
    for (int i = 1; i < n; i++) {
        for (int j = a[i]; j <= i + 1; j++) {
            dp[i][j] = (dp[i - 1][j - 1] + dp[i - 1][j] * j) % mod;
        }
        dp[i - 1][level]++;
        for (int j = 1; j < a[i]; j++) {
            dp[i][j] = (dp[i - 1][j - 1] + dp[i - 1][j] * j) % mod;
        }
    }
    int ans = 1;
    for (int i = 1; i <= n; i++) {
        (ans += dp[n - 1][i]) %= mod;
    }
    cout << ans;
    return 0;
}
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