Submission #519882

#	Time	Username	Problem	Language	Result	Execution time	Memory
519882		Vianti	Anagramistica (COCI21_anagramistica)	C++17	110 / 110	6 ms	1812 KiB

anagramistica

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;

const ll mod = 1e9 + 7;

ll fact[10000];

void precalc() {
    fact[0] = 0;
    fact[1] = 1;
    for (int i = 2; i < 10000; i++) {
        fact[i] = i * fact[i - 1];
        fact[i] %= mod;
    }
}

ll binpow(ll x, int p) {
    if (p == 0)return 1;
    if (p % 2 == 0) {
        ll res = binpow(x, p / 2);
        res *= res;
        res %= mod;
        return res;
    } else {
        return (x * binpow(x, p - 1)) % mod;
    }
}

ll inv(ll x) {
    return binpow(x, mod - 2);
}

ll C(ll a, ll b) {
    if (a == b)return 1;
    if (b == 0)return 1;
    ll res = fact[a];
    ll d = fact[b] * fact[a - b];
    d %= mod;
    res *= inv(d);
    res %= mod;
    return res;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    precalc();
    int n, k;
    cin >> n >> k;
    map<string, int> mp;
    for (int i = 0; i < n; i++) {
        string s;
        cin >> s;
        sort(s.begin(), s.end());
        mp[s]++;
    }
    vector<int> a;
    for (auto& el: mp) {
        a.push_back(el.second);
    }
    n = a.size();
    vector<vector<ll>> dp(n + 1, vector<ll>(k + 1, 0));
    dp[0][0] = 1;
    for (int i = 1; i <= n; i++) {
        vector<ll> b(a[i - 1] + 1, 0);
        for (int t = 0; t <= a[i - 1]; t++) {
            b[t] = C(a[i - 1], t);
            b[t] %= mod;
        }
        for (int j = 0; j <= k; j++) {
            for (int t = 0; t <= a[i - 1]; t++) {
                int cntpairs = t * (t - 1) / 2;
                if (cntpairs > j)continue;
                dp[i][j] += b[t] * dp[i - 1][j - cntpairs];
                dp[i][j] %= mod;
            }
        }
    }
    cout << dp[n][k] << endl;
}

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