1208. Legendary Teams Contest - Timus

#include <bits/stdc++.h>

using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int N;
    cin >> N;
    vector < vector < string > > a(N, vector < string >(3));
    for(int i = 0; i < N; ++i)
        for(int j = 0; j < 3; ++j)
            cin >> a[i][j];
    int ans = 1;
    for(int mask = (1 << N); mask > 0; --mask) {
        unordered_map < string , bool > M;
        int s = __builtin_popcount(mask);
        if(s > ans) {
            bool ok = true;
            for(int i = 0; (1 << i) <= mask && ok; ++i)
                if(mask & (1 << i))
                    for(int j = 0; j < 3 && ok; ++j)
                        if(M[a[i][j]])
                            ok = false;
                        else
                            M[a[i][j]] = true;
            if(ok)
                ans = s;
        }
    }
    cout << ans;
}