제출 #1053544

#제출 시각아이디문제언어결과실행 시간메모리
1053544VMaksimoski008Calvinball championship (CEOI15_teams)C++17
70 / 100
13 ms8468 KiB
#include <bits/stdc++.h>
using namespace std;

const int mod = 1e6 + 7;
const int LOG = 20;
const int maxn = 1e5 + 5;

int n;
vector<int> v;
int dp[1005][1005][2];

int f(int pos, int mx, int under) {
    if(pos == n + 1) return under;
    if(dp[pos][mx][under] != -1) return dp[pos][mx][under];

    long long ans = 0;

    if(under) {
        ans = (ans + 1ll * mx * f(pos+1, mx, 1)) % mod;
        if(mx+1 <= pos) ans = (ans + f(pos+1, mx+1, 1)) % mod;
    } else {
        for(int i=1; i<=min(pos, mx+1); i++) {
            if(!under && i > v[pos]) continue;
            ans = (ans + f(pos+1, max(mx, i), under|(i<v[pos]))) % mod;
        }
    }

    return dp[pos][mx][under] = ans;
}

signed main() {
    memset(dp, -1, sizeof(dp));

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

    cout << (f(2, 1, 0) + 1) % mod << '\n';
    return 0;
}
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