func_code_string: #include <bits/stdc++.h>   #pragma optimization_level 3   #pragma GCC optimize( Ofast,no-stack-protector,unroll-loops,fast-math,O3 )   using namespace std;   mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());   int main() {     cin.tie(0);     cout.tie(0);     cin.sync_with_stdio(0);     cout.sync_with_stdio(0);     ;     long long z;     cin >> z;     for (; z--;) {       long long a;       cin >> a;       vector<string> m(a);       int can[a];       set<string> s;       for (int q = 0; q < a; q++) {         cin >> m[q];         s.insert(m[q]);       }       for (int q = 0; q < a; q++) {         reverse(m[q].begin(), m[q].end());         can[q] = !s.count(m[q]);         reverse(m[q].begin(), m[q].end());       }       long long fl = 1;       vector<long long> n, t(4), msk(a);       int i = 0;       for (string &u : m) {         int mask = (u[0] ==  1 ) * 2 + (u.back() ==  1 ) * 1;         t[mask]++;         msk[i++] = mask;       }       if (!(t[1] + t[2]))         fl = t[0] == a || t[3] == a;       else {         long long ABS = abs(t[1] - t[2]), nd = t[2] > t[1] ? 2 : 1;         for (int q = 0; q < a && ABS > 1; q++) {           if (msk[q] != nd || !can[q]) continue;           ABS -= 2;           n.push_back(q + 1);         }         fl = ABS < 2;       }       if (!fl)         cout <<  -1 n ;       else {         cout << n.size() <<   n ;         for (long long i : n) cout << i <<    ;         cout <<   n ;       }     }   }   