recursivo-tle.cpp

#include <bits/stdc++.h>

using namespace std;

int n, k;
vector<int> v;
vector<vector<int>> boxes;

bool backtrack(int ik, int sum, int d_sum, int taken) {
    if (ik == k && sum == 0) {
        return true;
    } else if (ik < k && sum == d_sum) {
        return backtrack(ik + 1, 0, d_sum, taken);
    } else if (sum > d_sum) {
        return false;
    }
    for (int i = 0; i < n; i++) {
        if ((taken >> i & 1) == 0) {
            taken ^= 1 << i;
            boxes[ik].push_back(v[i]);
            bool rv = backtrack(ik, sum + v[i], d_sum, taken);
            if (rv)
                return true;
            boxes[ik].pop_back();
            taken ^= 1 << i;
        }
    }
    return false;
}

void solve() {
    int sum = 0;
    for (auto e : v) {
        sum += e;
    }
    if (sum % k != 0) {
        cout << "impossivel" << endl;
    } else if (backtrack(0, 0, sum / k, 0)) {
        for (int i = 0; i < k; i++) {
            cout << boxes[i].size() << ' ';
            for (int j = 0; j < (int) boxes[i].size(); j++) {
                cout << boxes[i][j];
                cout << (j < (int) boxes[i].size() - 1 ? ' ' : '\n');
            }
        }
    } else {
        cout << "impossivel" << endl;
    }
}

int main() {
    cin >> n >> k;
    v.resize(n);
    boxes.resize(k);
    for (int i = 0; i < n; i++) {
        cin >> v[i];
    }
    solve();

    return 0;
}