Submission #649208

#	Time	Username	Problem	Language	Result	Execution time	Memory
649208		boris_mihov	NoM (RMI21_nom)	C++17	21 / 100	503 ms	6288 KiB

Main

#include <algorithm>
#include <iostream>
#include <numeric>
#include <vector>
#include <set>

typedef long long llong;
const int MAXN = 2000 + 10;
const int MOD  = 1e9 + 7;
const int INF  = 1e9;

int n, m;
llong fact[MAXN];
llong var[MAXN][MAXN];
llong comb[MAXN][MAXN];
llong dp[2][MAXN][MAXN];
void solve()
{
    for (int i = 0 ; i <= n ; ++i)
    {
        comb[i][0] = 1;
    }

    fact[0] = 1;
    for (int i = 1 ; i <= n ; ++i)
    {
        fact[i] = (1LL * fact[i-1] * i) % MOD;
    }

    for (int i = 1 ; i <= n ; ++i)
    {
        for (int j = 1 ; j <= i ; ++j)
        {
            comb[i][j] = comb[i-1][j] + comb[i-1][j-1];
            if (comb[i][j] >= MOD) comb[i][j] -= MOD;
        }
    }

    for (int i = 0 ; i <= n ; ++i)
    {
        for (int j = 0 ; j <= i ; ++j)
        {
            var[i][j] = (1LL * comb[i][j] * fact[j]) % MOD; 
        }
    }

    dp[0][0][0] = 1;
    for (int i = 1 ; i <= m ; ++i)
    {
        int len = (2*n - i + 1) / m + (i != 1);
        for (int zeros = 0 ; zeros <= n ; ++zeros)
        {
            for (int ones = 0 ; ones <= n ; ++ones)
            {
                for (int addOnes = std::max(0, len - ones) ; addOnes <= std::min(len, zeros) ; ++addOnes)
                {
                    dp[i&1][zeros][ones] += (((((1LL * dp[!(i&1)][zeros - addOnes][ones + 2*addOnes - len] * comb[len][addOnes]) % MOD) * var[zeros][addOnes]) % MOD) * var[ones][len - addOnes]) % MOD;
                    if (dp[i&1][zeros][ones] >= MOD) dp[i&1][zeros][ones] -= MOD;
                }
            }
        }
    }

    int ans = dp[m&1][n][0];
    for (int i = 1 ; i <= n ; ++i)
    {
        ans *= 2;
        ans %= MOD;
    }
    

    std::cout << ans << '\n';
}

void read() 
{
    std::cin >> n >> m;
}

void fastIO()
{
    std::ios_base :: sync_with_stdio(0);
    std::cout.tie(nullptr);
    std::cin.tie(nullptr);
}

int main()
{
    fastIO();
    read();
    solve();

    return 0;
}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 0 / 13
• Subtask 4: 0 / 18
• Subtask 5: 0 / 48