Submission #715644

#	Time	Username	Problem	Language	Result	Execution time	Memory
715644		Farbod	Anagramistica (COCI21_anagramistica)	C++17	110 / 110	12 ms	6296 KiB

anagramistica

/*
*  In the name of God
*
*  Author: Farbod Doost
*  Last Modified: Mon, 27 Mar 2023 (14:38:55)
*
*/
#include <bits/stdc++.h>
using namespace std;

const int N = 2005;
const long long mod = 1e9 + 7;

long long fact[N], inv[N];

int n, k, cnt[N], T = 0;
map <string, int> mp;

long long dp[N][N];

long long p(long long n, long long r)
{
    if (r == 0)
        return 1;
    if (r == 1)
        return n;

    long long c = p(n, r / 2);
    return c * c % mod * p(n, r % 2) % mod;
}

long long C(int n, int r)
{
    return fact[n] * inv[r] % mod * inv[n - r] % mod;
}

signed main()
{
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);

    fact[0] = inv[0] = 1;
    for (int i = 1; i < N; i++)
        fact[i] = fact[i - 1] * i % mod,
        inv[i] = p(fact[i], mod - 2);

    cin >> n >> k;
    for (int i = 0; i < n; i++) {
        string s;
        cin >> s;

        sort(s.begin(), s.end());

        if (mp[s] == 0)
            mp[s] = ++T;
        cnt[mp[s]]++;
    }

    dp[0][0] = 1;
    for (int j = 0; j <= k; j++)
        for (int i = 1; i <= T; i++)
            for (int l = 0; l * (l - 1) / 2 <= j && l <= cnt[i]; l++)
                dp[i][j] += (dp[i - 1][j - l * (l - 1) / 2] * C(cnt[i], l) % mod),
                dp[i][j] %= mod;

    cout << dp[T][k];

    return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 30 / 30
• Subtask 3: 70 / 70