CCC 2026 S3 Common Card Choice

    1#include <bits/stdc++.h>
    2using namespace std;
    3using ll = long long;
    4using i128 = __int128;
    5const int inf = 1e9;
    6const ll INF = 1LL << 60; //❄️
    7int main() {
    8    ios::sync_with_stdio(0); cin.tie(0); 
    9    int n; cin >> n;
    10    vector<ll> v(n);
    11    for (int i = 0; i < n; i++) cin >> v[i];
    12    if (v[0] == -1) {
    13        int k = min(100, n / 4);
    14        cout << k << '\n';
    15        int cur = 1;
    16        for (int i = 0; i < k; i++) {
    17            cout << 2 << " " << 2 << '\n';
    18            cout << cur << " " << cur + 1 << '\n';
    19            cout << cur + 2 << " " << cur + 3 << '\n';
    20            cur += 4;
    21        }
    22        return 0;
    23    }
    24    auto out = [&](const vector<int> &a, const vector<int> &b) {
    25        cout << "YES" << '\n';
    26        cout << a.size() << " " << b.size() << '\n';
    27        for (int i = 0; i < a.size(); i++) {
    28            cout << a[i] << " \n"[i == a.size() - 1];
    29        }
    30        for (int i = 0; i < b.size(); i++) {
    31            cout << b[i] << " \n"[i == b.size() - 1];
    32        }
    33    };
    34    if (n < 5) { // 0 --> not used, 1 --> alice, 2 --> bob
    35        ll lim = 1;
    36        for (int i = 0; i < n; i++) lim *= 3;
    37        for (int mask = 0; mask < lim; mask++) {
    38            ll x = mask;
    39            vector<int> a, b;
    40            ll sum_a = 0, sum_b = 0;
    41            for (int i = 0; i < n; i++) {
    42                int c = x % 3;
    43                x /= 3;
    44                if (c == 1) {
    45                    a.push_back(i + 1);
    46                    sum_a += v[i];
    47                } else if (c == 2) {
    48                    b.push_back(i + 1);
    49                    sum_b += v[i];
    50                }
    51            }
    52            if (a.size() == 0 || b.size() == 0 || a.size() == n || b.size() == n) continue;
    53            int g = gcd(sum_a, sum_b);
    54            if (g > 1) {
    55                out(a, b);
    56                return 0;
    57            }
    58        }
    59        cout << "NO" << '\n';
    60        return 0;
    61    }
    62    vector<int> even_indx, odd_indx;
    63    for (int i = 0; i < 5; i++) {
    64        if ((v[i] & 1) == 0) even_indx.push_back(i + 1);
    65        else odd_indx.push_back(i + 1);
    66    }
    67    if (even_indx.size() >= 4) {
    68        vector<int> a = {even_indx[0], even_indx[1]}, b = {even_indx[2], even_indx[3]};
    69        out(a, b);
    70        return 0;
    71    } else if (odd_indx.size() >= 4) {
    72        vector<int> a = {odd_indx[0], odd_indx[1]}, b = {odd_indx[2], odd_indx[3]};
    73        out(a, b);
    74        return 0;
    75    } else if (even_indx.size() == 3 && odd_indx.size() == 2) {
    76        vector<int> a = {even_indx[0], even_indx[1]}, b = {odd_indx[0], odd_indx[1]};
    77        out(a, b);
    78        return 0;
    79    } else if (even_indx.size() == 2 && odd_indx.size() == 3) {
    80        vector<int> a = {odd_indx[0], odd_indx[1]}, b = {even_indx[0], even_indx[1]};
    81        out(a, b);
    82        return 0;
    83    }
    84    return 0;
    85}