Submission #850363

#	Time	Username	Problem	Language	Result	Execution time	Memory
850363		serifefedartar	Magneti (COCI21_magneti)	C++17	110 / 110	229 ms	219220 KiB

Main

#include <bits/stdc++.h>
using namespace std;
 
#define fast ios::sync_with_stdio(0);cin.tie(0);
#define s second
#define f first
typedef long long ll;
const ll MOD = 1e9 + 7;
const ll LOGN = 20;
const ll MAXN = 24000;

ll expo(ll a, ll b) {
    ll res = 1;
    while (b) {
        if (b & 1)
            res = (res * a) % MOD;
        a = (a * a) % MOD;
        b /= 2;
    }
    return res;
}
ll fact[MAXN], inv[MAXN]; 
ll dp[55][55][MAXN];

ll nCr(ll n, ll r) {
    if (r > n)
        return 0LL;
    return ((fact[n] * inv[r]) % MOD * inv[n-r]) % MOD;
}

ll dist(ll item, ll plc) {
    return nCr(item + plc - 1, item);
}

vector<ll> seq;
int main() {
    fast
    fact[0] = inv[0] = 1;
    for (ll i = 1; i < MAXN; i++) {
        fact[i] = (fact[i-1] * i) % MOD;
        inv[i] = expo(fact[i], MOD-2); 
    }

    ll N, L;
    cin >> N >> L;

    seq = vector<ll>(N);
    for (int i = 0; i < N; i++)
        cin >> seq[i];
    sort(seq.begin(), seq.end());

    dp[1][1][1] = 1;
    for (int i = 2; i <= N; i++) {
        for (int open = 1; open <= N; open++) {
            for (int len = 1; len <= L; len++) {
                dp[i][open+1][len + 1] = (dp[i][open+1][len + 1] + dp[i-1][open][len]) % MOD;
                dp[i][open][len + seq[i-1]] = (dp[i][open][len + seq[i-1]] + 2 * open * dp[i-1][open][len]) % MOD;

                if (open != 1)
                    dp[i][open-1][len + 2 * seq[i-1] - 1] = (dp[i][open-1][len + 2 * seq[i-1] - 1] + open * (open-1) * dp[i-1][open][len] % MOD) % MOD;
            }
        }
    }

    ll ans = 0;
    for (int d = 1; d <= L; d++) {
        ll ways = dp[N][1][d];
        ans = (ans + ways * dist(L - d, N+1)) % MOD; 
    }
    cout << ans << "\n";
}

• Subtask 1: 10 / 10
• Subtask 2: 20 / 20
• Subtask 3: 30 / 30
• Subtask 4: 50 / 50