abc 314 B
实现起来很复杂，参考了jiangly的写法，学到了很多，对于简单题，如果时间复杂度允许，用更多直接的模拟（如果手速足够）比想巧方法要快得多，也容易得多

#include <bits/stdc++.h>

using i64 = long long;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int N;
    std::cin >> N;

    std::vector<std::vector<int>> A(N);
    for (int i = 0; i < N; i++) {
        int C;
        std::cin >> C;
        A[i].resize(C);
        for (int j = 0; j < C; j++) {
            std::cin >> A[i][j];
        }
    }

    int X;
    std::cin >> X;

    std::vector<int> p;
    for (int i = 0; i < N; i++) {
        if (std::find(A[i].begin(), A[i].end(), X) != A[i].end()) {
            p.push_back(i);
        }
    }

    if (p.empty()) {
        std::cout << 0 << "\n";
        return 0;
    }

    int mn = 1E9;
    for (auto i : p) {
        mn = std::min(mn, int(A[i].size()));
    }
    std::vector<int> ans;
    for (auto i : p) {
        if (A[i].size() == mn) {
            ans.push_back(i);
        }
    }
    std::cout << ans.size() << "\n";
    for (auto i : ans) {
        std::cout << i + 1 << " \n"[i == ans.back()];
    }

    return 0;
}

#include <bits/stdc++.h>

using namespace std;

typedef long long LL;

int main()
{
    std::ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N;
    cin >> N;

    vector<vector<int>> a(N);

    for (int i = 0; i < N; i ++)
    {
        int c;
        cin >> c;
        a[i].resize(c);

        for (int j = 0; j < c; j ++)
        cin >> a[i][j];
    }

    int x;
    cin >> x;

    vector<int> p;

    for (int i = 0; i < N; i ++)
    {
        if (find(a[i].begin(), a[i].end(), x) != a[i].end()) p.push_back(i);
    }

    if (p.empty())
    {
        cout << 0 << endl;

        return 0;
    }

    int mn = 1E9;

    for (auto i : p)
    {
        mn = min(mn, (int) a[i].size());
    }

    vector<int> ans;

    for (auto i : p) if (mn == a[i].size()) ans.push_back(i);

    cout << ans.size() << endl;

    for (auto i : ans) cout << i + 1 << ' ';

    cout << endl;

    return 0;
}

abc 313 B

要点是两两关系，要排出高低，只有最强者没有高于他的