哪里错了，提示是超时 int main() {     int n, m, q;     int count = 0;     set<int> s;     cin >> n >> m;     vector<int> vec;     for (int i = 0; i<n; ++i) {         int k = 0;         cin >> k;         if (s.count(k) == 0) {             s.insert(k);             ++count;         }         vec.push_back(count);     }     cin >> q;     for (int i = 0; i<q; ++i) {         int t1, t2;         cin >> t1 >> t2;         int res = 1 + vec[t2 - 1] - vec[t1 - 1];         cout << res << endl;     }     return 0; }